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UNIVERSITY  OF  ILLINOIS 

Agricultural  Experiment  Station 


BULLETIN  No.  189 


PARASITIC  RHIZOCTONIAS  IN  AMERICA 


BY  GEOEGE  L.  PELTIER 


URBANA,  ILLINOIS,  JUNE,  1916 


CONTENTS  OF  BULLETIN  No.  189 

PAGE 

Introduction 283 

General  Historical   Account 283 

General  Characters  of  Ehizoctonia 286 

Distribution  of  Ehizoctonia  in  the  United  States 292 

Distribution  of  Ehizoctonia  in  Canada 306 

Distribution  of  Ehizoctonia  in  South  America  and  the  West  Indies 306 

Distribution  of  Ehizoctonia  in  Europe 306 

Distribution  of  Ehizoctonia  in  India  and  Australia 308 

Plan  of  Procedure ' 308 

Symptoms  of  Ehizoctonia  Disease  on  Various  Hosts.  .  . 308 

Inoculation  Experiments 337 

Discussion  of  Inoculation  Experiments 358 

Growth  on  Media 364 

Measurement  of  Mycelial  Cells 370 

Soil  Survey  of  Ehizoctonia 372 

Parasitism  of  Rhisoctonia  Solani  Kiihn 375 

Summary    376 

Appendix    378 

Bibliography    386 


FIG.   1. — CARNATION   STEM  EOT  CAUSED  BY  EMzoctonia  Solani 


PARASITIC  RHIZOCTONIAS  IN  AMERICA* 

BY  GEORGE  L.  PELTIER,  ASSOCIATE   IN  FLORICULTURAL  PATHOLOGY 


One  of  the  most  serious  and  troublesome  diseases  which  must  be 
contended  with  by  carnation  growers  in  this  country  is  the  so-called 
"stem  rot"  due  to  the  fungus  Rhizoctonia.  In  1911  a  study  of  this 
disease  was  undertaken  at  the  University  of  Illinois  by  Mr.  H.  W.( 
Anderson,  at  that  time  Assistant  in  Floricultural  Pathology  and  now 
Professor  of  Botany  in  Wabash  College.  Since  July,  1912,  when  Mr. 
Anderson  left,  a  thoro  investigation  of  those  diseases  of  vegetable, 
field,  and  floricultural  crops  which  are  caused  by  Rhizoctonia  has 
been  conducted  by  the  writer,  the  primary  object  being  to  determine 
whether  infection  is  brought  about  by  one  or  by  more  than  one  race  or 
species  of  this  fungus.  The  results  of  this  phase  of  the  work  are  pre- 
sented in  the  following  pages.  Extensive  studies  have  also  been  made 
of  stem  rot,  with  a  view  to  publishing  at  a  later  date. 

GENERAL  HISTORICAL  ACCOUNT 

The  first  description  of  Rhizoctonia  was  given  by  Duhamel,33  who  in 
1728  found  it  causing  a  disease  of  saffron  (Crocus  sativus)  in  southern 
France.  The  diseased  bulbs  were  thickly  covered  with  a  reddish  vio- 
let network  of  hyphae  which  spread  out  into  the  surrounding  soil,  with 
knot-like  swellings  here  and  there  in  the  mycelial  network.  Duhamel 
conceived  these  swellings  (tubercules)  to  be  the  individual  plants  and 
the  hyphae  to  be  the  roots,  and  named  the  fungus  Tiiberoides. 

Almost  sixty  years  later  (1785)  another  French  investigator,  Fou- 
geroux  de  Bondaroy,23  mentioned  that  asparagus  that  was  grown  on 
land  in  which  diseased  saffron  bulbs  had  been  previously  grown  suf- 
fered from  this  same  disease.  Bulliard11  in  1791  numbered  it  among 
the  Truffles  and  named  it  Tuber  parasiticum.  Ten  years  afterward  Per- 
soon82  placed  the  fungus  in  the  genus  Sclerotium  and  called  it  Sclero- 
tium  Crocorum. 

De  Candolle,24  who  discovered  a  similar  disease  on  lucerne,  gave  to 
the  fungus  the  name  Rhizoctonia.  Later  he  distinguished  three  species, 
R.  Crocorum,  R.  Medicaginis,  and  R.  Mali.  Nees70  in  1817  referred 

"The  results  presented  in  this  bulletin  formed  part  of  a  thesis  submitted  by 
the  author  to  the  Graduate  School  of  the  University  of  Illinois  in  partial  fulfil- 
ment of  the  requirements  for  the  degree  of  doctor  of  philosophy  in  botany,  May, 
1915.  Revised  to  date  of  issuance. 

283 


284  BULLETIN  No.  189  [June, 

to  a  fungus  attacking  crocus  as  Thanatophytum  Crocorum.  This  ap- 
pears, from  his  description  and  figures,  to  have  been  Rhizoctonia.  A 
new  species  of  Rhizoctonia  was  described  in  France  by  Duby20  as  Rhi- 
zoctonia Allii  on  Allium  ascalonicum.  In  1843  Leveille65  noted  a  simi- 
lar Rhizoctonia  on  Rubia  tinctorum,  Solarium  tuberosum,  Pliaseolus, 
and  Tulipa,  without  attempting  to  place  it  under  any  particular 
species.  In  1851  the  Tulasne  brothers134  classified  all  the  forms  of 
Rhizoctonia  as  a  single  species,  Rhizoctonia  violacea,  a  classification 
which  has  been  adopted  by  a  number  of  writers.  Rhizoctonia  on  cro- 
cus was  reported  in  Germany  in  1858  by  Kiihn.64  He  also  found  this 
same  fungus,  which  he  identified  as  R.  Hedicaginis,  on  sugar  beet.  At 
the  same  time  he  described  a  new  species  of  Rhizoctonia  on  potato, 
which  he  clearly  distinguished  from  the  above  species  and  to  which  he 
gave  the  name  R.  Solani. 

In  the  United  States,  Rhizoctonia  was  first  reported  by  Webber137 
in  1890  on  the  roots  of  alfalfa  in  Nebraska.  He  listed  the  fungus  as 
Rhizoctonia  Medicaginis  DC.  The  first  extended  account  of  Rhizoc- 
tonia in  the  United  States  was  given  by  Pammel,76  who  found  it  caus- 
ing a  serious  disease  of  beets  in  Iowa.  Later,  Atkinson3  observed 
Rhizoctonia  causing  damping-off  of  cotton  seedlings,  and  following 
that,  of  a  number  of  other  kinds  of  seedlings.  In  1901  Duggar  and 
Stewart32  added  a  large  number  of  hosts  subject  to  Rhizoctonia  attack. 
Many  observations  of  other  hosts  and  in  new  localities  have  since  been 
made  until  at  the  present  time  Rhizoctonia  has  been  found  on  one  or 
more  hosts  in  practically  every  state  in  this  country.  It  has  also  been 
reported  from  Canada,  the  West  Indies,  South  America,  India,  and 
Australia,  so  that  it  may  be  regarded  as  a  truly  cosmopolitan  fungus. 

Duggar,8  in  an  article  published  since  this  manuscript  was  com- 
pleted, brings  out  the  fact  that  the  violet  root  felt  fungus,  commonly 
known  in  Europe  and  the  United  States  as  R.  violacea,  should  be  re- 
ferred to  as  R.  Crocorum,  (Pers.)  DC.  He  states  that  unfortunately 
this  name  has  priority  over  the  more  descriptive  name  R.  violacea. 
Under  R.  Crocorum  (Pers.)  DC.,  Duggar  lists  the  following  pro- 
visional synonymy: 

Tuber  parasiticum  Bull.  (1791) 
Sclerotium  Crocorum  Pers.   (1801) 
Ehizoctonia  Crocorum  DC.  (1815) 
Rhizoctonia  Medicaginis  DC.    (1815) 
Thanatophytum  Crocorum  Nees  (1816) 
Tuber  Croci  Duby  (1830) 
Ehizoctonia  Rubice  Dene.  (1837) 
Ehizoctonia  Dauci  Eabenh.   (1859) 
Ehizoctonia  violacea  Tul.  (1862) 
Ehizoctonia  Asparagi  Fckl.  [non  Fr.]   (1869) 
Hypochnus  violaceus  Eriks.  (1913) 


•Duggar,  B.  M. :  Ehizoctonia  Crocorum  (Pers.)  DC.  and  E.  Solani  Kiihn 
(Corticium  vagum  B.  &  C.)  with  Notes  on  Other  Species.  Ann.  Mo.  Bot.  Gard., 
2,  403-458,  9  figs.,  Sept.,  1915. 


1916]  PARASITIC  RHIZOCTONIAS  IN  AMERICA  285 

Under  R.  Solani  Kiihn  (Corticium  vagum  B.  &  C.),  the  form  com- 
monly found  in  this  country  and  to  a  less  extent  in  Europe,  and  the 
name  generally  used  by  American  authors,  Duggar  gives  the  following 
synonymy : 

Ehizoctonia  Betce  Eidam  [non  Kiihn]   (1887) 
Ehizoctonia  Napcece  West.     (1846) 
Ehizoctonia  Eapoe  West.  (1852) 
Hypochnus  Solani  Prill.  &  Del.  (1891) 

Duggar  states  further  that  with  the  evidence  at  hand  a  number  of 
species  of  Rhizoctonia  described  from  Europe  may  be  excluded  from 
the  genus,  while  several  species  are  doubtful.  He  adds  that  in  all 
probability  the  six  species  described  from  America,  listed  in  Saccardo, 
may  also  be  excluded,  altho  a  more  critical  study  of  material  is  needed. 

Many  attempts  have  been  made  to  connect  the  sterile  fungus  Rhi- 
zoctonia with  a  perfect  stage.  Fuckel43  in  1869  stated  that  the  ascomy- 
cete  Byssothesium  circinans  Fkl.  (LeptospJiceria  circinans  Sacc.)  was 
the  perfect  form.  However,  beyond  the  association  of  these  two  forms 
on  decaying  stems  of  Medicago  sativa,  there  were  no  signs  of  their  con- 
nection. The  same  observation  was  also  recorded  by  Prunet,90  but  again 
with  no  more  conclusive  proof  than  the  presence  of  the  two  forms  on 
the  same  plant.  Massee66  considered  Rhizoctonia  as  representing  the 
vegetative  condition  of  Rosellinia,  because  of  the  fact  that  the  struc- 
ture and  color  of  the  mycelium  and  the  general  habit  of  Rhizoctonia 
resembles  that  of  the  Rosellinia  quercina  Hartig  and  other  destructive 
parasites  belonging  to  that  genus.  He  had  no  further  evidence,  how- 
ever, to  support  this  supposition. 

During  the  summer  of  1913,  Cook,20  while  examining  tubers  af- 
fected with  Rhizoctonia,  found  a  sclerotium  that  contained  a  mass  of 
well-developed  asci  bearing  spores.  The  mycelium  .of  the  sclerotium 
was  characteristic  of  Rhizoctonia  and  the  asci  appeared  to  arise  di- 
rectly from  it ;  this  point,  however,  could  not  be  determined  with  any 
degree  of  certainty. 

In  1891  Prillieux  and  Delacroix89  described  a  basidiomycete,  Hy- 
pochnus Solani,  and  altho  at  the  time  they  did  not  associate  it  with 
Rhizoctonia,  it  has  been  accepted  by  a  number  of  European  writers  in 
recent  years  as  the  perfect  stage  of  R.  Solani. 

In  1897  Frank41  reported  Rhizoctonia  violacea  as  attacking  grape- 
vines, and  since  a  Thelephora  was  found  associated  with  it,  he  pro- 
posed the  name  Thelephora  Rhizoctonice. 

In  1903  Rolfs,93  working  with  the  Rhizoctonia  disease  of  potatoes 
in  Colorado,  found  constantly  associated  with  this  fungus  a  basidiomy- 
cete which  Dr.  E.  A.  Burt  identified  as  Corticium  vagum  B.  &  C.,  var. 
Solani.  He  was  able  to  trace  the  connection  between  the  two  forms, 
and  completed  his  evidence  when  he  obtained  cultures  of  Rhizoctonia 
from  single  spores  of  the  Corticium  stage. 


286 


BULLETIN  No.  189 


[June, 


Eriksson38  has  described  a  new  combination,  Hypoclinus  viola- 
ceus  (Tul.)  Eriks.,  which  he  believes  is  the  perfect  stage  of  Rhizoctonia 
violacea  Tul.  However,  beyond  association  on  different  plants  in 
the  same  field,  he  appears  to  have  no  further  evidence  to  show  that 
the  perfect  stage  which  he  found  on  a  number  of  weeds  is  connected 
with  R.  violacea,  found  on  a  number  of  root  crops. 

GENERAL  CHARACTERS  OF  RHIZOCTONIA 

The  morphological  characters  of  Rhizoctonia  Solani  Kiihn  vary 
with  the  age  of  the  mycelium.  The  young  hyphas  branch  at  an  acute 
angle  from  the  parent  hypha,  subsequently  lying  parallel  to  it.  A 
constriction  is  shown  at  the  point  of  union,  and  a  septum  is  generally 
laid  down  a  short  distance  from  this  point.  The  threads  are  colorless 
and  vacuolate.  With  age  the  hyphae  lie  more  at  a  right  angle  with  the 
main  axis,  showing  less  constriction.  They  deepen  in  color  into  a  yel- 
lowish and  then  a  rather  deep  brown,  becoming  more  or  less  granular 
and  empty.  (Fig.  2.)  Fusion  of  hyphae  is  very  common  and  can  be 
observed  in  any  young  culture  of  the  fungus.  It  occurs  either  between 
hyphae  of  the  same  parent  mycelium  or  between  hyphae  from  separate 
colonies  (Fig.  2). 

On  many  hosts  a  short  tufted  or  bushy  growth  of  the  mycelium 
may  occur  with  some  strains.  This  tufted  growth  is  likewise  present 


FiG.  2, —  (1)  YOUNG  HYPH.*:  OP  Ehisoctonia  Solani;   (2)  OLD,  BROWN,  AND  EMPTY 

OF  Rhizoctonia  Solani 


1916]  PARASITIC  RHIZOCTONIAS  IN  AMERICA  287 

in  cultures  of  the  strains  that  produce  such  growth  on  the  host  plants. 
The  tufts  are  composed  of  brown  hyphae,  closely  septate,  constricted 
at  the  septa,  and  often  branching  in  an  irregular  manner. 

Sclerotia  in  cultures  first  appear  as  small,  soft,  white  masses  of 
hyphae.  Later  they  become  larger  and  turn  dark  and  hard.  Study  of 
sclerotia  at  different  ages  shows  that  they  are  of  uniform  structure  com- 
posed entirely  of  masses  of  irregular  and  barrel-shaped  cells  which 
break  up  into  sections  of  one  or  several  cells  (Fig.  3).  These  shortened 
hyphal  cells  function  as  conidia  and  germinate  readily  under  suitable 
conditions.  Germination  generally  takes  place  by  the  protrusion  of  a 
tube  thru  the  septum  of  a  cell  where  it  has  broken  away  from  an  adja- 
cent cell.  In  some  cases  the  hyphse  of  the  germinating  cells  pass  thru 
adjacent  cells,  which  are  apparently  empty.  Occasionally  these  irreg- 
ular and  barrel-shaped  cells  germinate  equatorially  instead  of  at  the 
poles.  After  the  germ  tube  has  grown  out  some  distance,  it  becomes 
narrowed  near  the  germinating  cell  and  a  septum  is  laid  down.  The 
mycelium  then  develops  in  the  usual  manner  (Fig.  4). 

The  formation  of  sclerotia  in  nature  is  rather  common  on  majiy 
hosts.  The  best  known  examples  are  those  formed  on  the  potato  tuber. 
The  size  and  shape  of  the  sclerotia  vary  considerably.  On  potatoes 
they  are  small,  about  1  to  5  millimeters,  and  are  generally  flat.  On 
carnation  plants  they  may  reach  a  diameter  of  5  to  8  millimeters. 
When  the  fungus  is  grown  on  soil  in  pure  culture,  they  become  5  to  6 
centimeters  in  diameter  (Fig.  5). 

The  sporiferous  stage  of  Rhizoctonia  Solani  was  first  observed  in 
this  country  by  Rolfs93  in  1903,  on  potato  stems.  It  was  described  by 
Burt  94  as  Corticium  vagum  B.  &  C.,  var.  Solani"  In  Europe  this  same 
fungus  is  generally  known  as  Hypochnus  Solani  Prill.  &  Del." 

Altho  the  writer  has  observed  Rliizoctonla  Solani  on  seventy-five 
species  of  plants,  including  weeds  and  field j  vegetable,  ornamental,  and 
floricultural  crops,  growing  under  diverse  conditions  and  at  different 
times  of  the  year,  for  the  past  three  seasons,  it  was  not  until  the  spring 
of  1915  that  he  found  the  Corticium  stage.  It  was  then  observed  in 
his  home  garden  on  bean,  beet,  radish,  potato,  parsnip,  carrot,  chard, 
spinach,  pea,  plantain,  and  pigweed.  This  stage  was  also  found  on 
winter  vetch  growing  on  newly  plowed  land,  on  carnation  plants,  and 
on  a  number  of  annual  and  perennial  plants.  In  some  cases  patches  of 
soil  well  protected  from  desiccation  were  covered  with  the  ashy  gray 
mycelium  of  the  perfect  stage. 

•In  a  recent  letter  from  Dr.  Burt,  he  states :  "  I  do  not  now  believe  that  there 
is  even  a  varietal  difference  between  Corticium  vagum  B.  &  C.  and  that  on  the 
potatoes ;  hence  I  shall  drop  var.  Solani. ' ' 

bln  his  monograph  on  the  Thelephoracece,  Burt12  limits  Hypochnus  to  resupi- 
nate  species  with  colored,  echinulate  spores,  while  under  Corticium  he  includes 
species  always  resupinate,  which  have  colorless  spores  and  lack  cystidia.  Accord- 
ing to  Burt 's  classification,  Hypochnus  Solani  Prill.  &  Del.  becomes  a  synonym 
under  Corticium  vagum  B.  &  C. 


288 


BULLETIN  No.  189 


[June, 


FIG.  3. —  (1)  YOUNG,  BARREL-SHAPED  CELLS  WHICH  COMPOSE  THE  SCLEROTIA  OF 
Ehizoctonia  Solani;  (2)  OLDER,  EMPTY  CELLS  FROM  THE  SCLEROTIA 


FIG.  4. — GERMINATING  SCLEROTIAL  CELLS  OF  Shizoctonin  Sohmi 


1916] 


PARASITIC  EHIZOCTONIAS  IN  AMERICA 


289 


290  BULLETIN  No.  189  [June, 

The  presence  of  the  Corticium  stage  seems  to  depend  on  climatic 
conditions.  A  cool  season  with  an  abundance  of  moisture  is  appar- 
ently essential  for  its  development  in  the  field.  This  stage  is  gener- 
ally found  on  plant  .tissues  that  are  perfectly  healthy ;  it  is  in  no  way 
injurious  to  them.  Some  cases  have  been  found  where  it  had  devel- 
oped on  stems  almost  cut  off  by  Rhizoctonia,  but  in  no  instance  has 
the  writer  seen  it  form  directly  on  a  lesion  or  on  injured  tissue.  (See 
Figs.  6  and  7.) 

The  development  of  the  Corticium  stage  may  be  described  as  fol- 
lows :  The  dark  brown  hyphae  of  the  sterile  stage  gather,  usually  at  the 
base  of  the  plant,  and  from  them  arises  an  ashy  gray  mycelium,  which 
forms  a  fine  network  around  the  stem.  The  development  is  usually 
faster  where  a  little  soil,  thrown  up  by  the  rains,  has  formed  a  film 
around  the  stem.  The  extent  of  this  fruiting  layer  varies,  but  it  may 
proceed  several  centimeters  up  the  stem.  It  is  so  lightly  attached  to 
the  plant  that  it  may  easily  be  rubbed  off.  As  it  becomes  old,  it  cracks 
and  falls  off. 

The  outer  hyphae  of  the  fruiting  layer  bear  club-shaped  basidia 
with  four  sterigmata  and  spores.  Cystidia  are  lacking.  The  spores 
are  colorless,  oval  to  ovate,  and  have  pointed  bases.  The  usual  spore 
measurement  varies  from  9  to  14  /*  by  6  to  8  /*. 

Cultures  of  Rhizoctonia  from  single  spores  of  the  Corticium  stage 
have  been  obtained  both  by  dilution  methods  and  by  the  method  used 
by  Rolfs,94  which  consists  in  placing  a  stem  covered  with  the  fruiting 
stage  over  an  open  petri  dish  containing  a  nutrient  agar,  and  allowing 
the  spores  to  drop  on  the  agar. 

Another  fungus  belonging  to  the  genus  Corticium,  C.  ochra- 
leucum  (Noack)  Burt  (see  footnote  b,  page  287),  found  in  the  United 
States  by  Stevens  and  Hall117'119  on  pomaceous  fruits,  has  been  care- 
fully examined  by  the  writer.  The  mycelium  of  this  species  corre- 
sponds in  many  respects  to  that  of  R.  Solani  and  the  development  of 
the  perfect  stage  is  similar  to  the  development  of  the  Corticium  stage 
of  that  species.  It  appears  that  these  two  species  are  very  closely  re- 
lated, but  are  entirely  distinct  forms. 

Duggar,"  who  has  had  an  opportunity  to  study  R.  Crocorum 
(Pers.)  DC.  more  at  length,  gives  the  following  description  of  this 
species  in  his  recent  work : 

"The  external,  general  hyphae  are  more  or  less  different  in  form  and  appear- 
ance with  age.  The  younger  hyphae  are  usually  dilutely  violaceous  with  a  pigment 
which  may  be  decolorized  by  the  application  of  acidulated  water.  The  protoplasm 
is  dense  towards  the  tips  of  branches  and  vacuolated  farther  away.  The  hyphae 
are  somewhat  flexuous,  branched  (sometimes  closely),  with  the  branches  arising 
at  right  angles  to  the  main  hypha,  and  with  a  partition  wall  laid  down  at  not 
over  10  fj.  distant.  With  age  the  hyphae  become  rigid,  somewhat  less  in  diameter, 
4—8  ft,  the  branching  is  distant,  and  these  branches  readily  break  off  at  the  first 
partition  wall.  At  the  point  of  union  the  diameter  is  uniform  with  the  main 

*See  footnote,  page  284. 


ID  16] 


PARASITIC  HHIZOCTONIAS  IN  AMERICA 


291 


FIG.  6. — GREEN  TOMATO  SHOWING  THE  SUPERFICIAL  ASHY  GRAY  MYCELIUM  OF  Cor- 
ticium  vagum  B.  &  C.  PRESENT  AT  THE  POINT  WHERE   THE  TOMATO  TOUCHED 

THE   SOIL 


FIG.  7. — ENLARGED  VIEW  OF  A  SECTION  OF  FIG.  6,  SHOWING  THE  DARK  STRANDS  OF 
HYPH^E  AND  SMALL,  SPHERICAL,  BROWNISH  SCLEROTIA  OF  Ehizoctonia  Solani 
KUHN  WITH  THE  ASHY  GRAY  NETWORK  OF  MYCELIUM  OF  Corticium  vagum 

B.  &  C.   (5x) 


292  BULLETIN  No.  189  [June. 

hypha.  The  partition  walls  are  distant,  often  120-200  /j.  apart.  The  walls  now 
possess  the  violet-brown  pigment  and  in  the  lumen  little  or  no  protoplasm  is  ob- 
servable. 

"The  internal  mycelium  is  likewise  branched,  septate,  often  associated  into 
loose  strands,  passing  between  the  cells  or  traversing  them.  In  the  early  stages 

of  the  disease,  so  far  as  reported,  these  internal  hypha3  are  nearly  colorless 

and  are  generally  of  less  diameter  than  those  constituting  the  external  mat. 

" the  hyphae  constituting  the  external  mantle  may  be  uniformly  dis- 
tributed, as  is  the  case  usually  when  the  fungus  attacks  fleshy  roots  or  tubers,  or 
they  may  also  form  a  number  of  aggregates  having  the  appearance  of  loose  or  root- 
like  strands." 

The  infection  cushions  are  distributed  over  infected  roots.  ' '  The  external 
hyphae  are  for  the  most  part  similar  to  those  of  the  general  mycelium,  but  there 
occur  also  branches  in  which  the  cells  are  short  and  swollen,  sometimes  resembling 

a  short  chain  of  spores The  medullary  portion  of  younger  cushions  is 

made  up  of  finer,  almost  colorless  hyphae,  and  it  is  this  type  which  enters — strand- 
like — the  cortical  tissues  of  the  root,  destroying  particularly  the  cambium  and 
younger  phloem  regions.  In  the  later  stages  of  development  it  will  be  found  that 
the  cushions  seem  to  extend  considerably  into  the  cortex,  and  more  of  the  hyphae 
are  colored." 

' '  The  true  sclerotia  are  flattened  or  rounded  bodies  varying  in  diameter  from 
a  few  millimeters  to  several  centimeters.  When  mature  they  are  of  a  deep  violet- 
brown  and  are  thickly  clothed  with  a  persistent  velvety  felt,  externally  of  the  same 
color  as  the  root-investing  hyphae,  but  ^darkening  further  in.  Among  the  surface 
hyphae  of  the  sclerotia  as  well  as  of  the  'infection  cushions'  are  found  chains 
of  enlarged  cells  quite  distinct  from  the  enlarged  cells  of  E.  Solani.  The  sclerotia, 
as  noted  previously,  are  always  connected  with  the  root  felt  by  large  hyphal 
strands. 

" a  sclerotium  consists  of  fairly  compact  tissue  made  up  of  cells 

often  considerably  branched  and  sometimes  curiously  lobed." 

DISTRIBUTION  OF  RHIZOCTONIA  IN  THE  UNITED  STATES 

In  Table  1  is  presented  a  list  of  those  species  and  sub-species 
which  have  been  reported  as  being  susceptible  to  R.  Solani  in  the 
United  States.  It  is  obvious  that  as  long  as  investigations  on  this  dis- 
ease are  continued,  such  a  list  cannot  be  regarded  as  complete  or  final. 
It  may  be  noted  that  plants  belonging  to  the  families  AmarantTiacece, 
Caryophyllacece,  Cruciferce,  Leguminosce,  Solanaceoe,  and  Composites 
are  especially  susceptible  to  this  fungus.  Under  favorable  conditions 
it  can  attack  plants  in  these  families  at  any  stage,  from  seedlings  or 
cuttings  to  older  plants,  when  grown  either  in  the  field  or  in  the  green- 
house. About  fifty  important  families  of  flowering  plants  are  repre- 
sented, several  gymnosperms,  and  Equisetum,  one  of  the  Pterido- 
phytes.  The  list  includes  a  number  of  monocotyledons,  which  for- 
merly were  reported  as  being  not  susceptible  to  Rhizoctonia.  Among 
the  dicotyledons  are  many  annuals  and  perennials,  including  herbs 
and  woody  plants,  as  well  as  most  of  the  greenhouse  and  garden 
plants,  field  crops,  and  weeds. 

R.  Crocorum,  as  will  be  seen  in  Table  la,  has  been  reported  so  far 
in  this  country  from  only  a  few  scattered  states.  It  is  probable  that 
as  investigations  continue  this  fungus  will  be  found  in  many  other 
localities. 


1916] 


PARASITIC  RHIZOCTONIAS  IN  AMERICA 


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306  BULLETIN  No.  189  [June, 

DISTRIBUTION  OF  RHIZOCTONIA  IN  CANADA 

In  a  letter  to  the  writer,  Dr.  H.  T.  Giissow  of  the  Central  Experi- 
mental Farm,  Ottawa,  Canada,  stated  that  he  had  observed  Rhi- 
zoctonia  Solani  on  potato,  pea,  sweet  pea,  and  aster.  That  the  stem 
rot  of  carnation  also  occurs  in  Canada  is  shown  in  a  paper  read  by 
John  Morgan  of  Hamilton,  Ontario,  before  the  Canadian  Horticul- 
tural Association  at  Guelph,  in  August,  1906. 

DISTRIBUTION  OF  RHIZOCTONIA  IN  SOUTH  AMERICA  AND 
THE  WEST  INDIES 

The  following  list  of  plants  reported  as  susceptible  to  'R.  Solani 
in  South  America  and  the  West  Indies,  with  character  of  injury,  has 
been  compiled  from  Cook's19  Diseases  of  Tropical  Plants: 

Bean Damping-off,  dry  rot  of  stem,  and  pod  rot 

Beet Root  disease 

Cotton Damping-off  and  sore  shin 

Cucumber Damping-off 

Lettuce Damping-off 

Melon Damping-off 

Nursery  stock Damping-off 

Pea Root  and  stem  rot 

Potato On  stem  and  tubers 

Seedlings Damping-off 

Sweet  potato Root  rot 

Tobacco Seed-bed  rot 

Tomato Rosette  and  fruit  rot 

DISTRIBUTION  OF  RHIZOCTONIA  IN  EUROPE 

Despite  the  wide  distribution  of  Rhizoctonia  in  Europe,  the  nomen- 
clature of  the  species  is  in  a  very  confused  state.  Some  writers  under- 
stand Rhizoctonia  Crocorum  (Pers.)  DC.  to  include  several  species, 
while  others  treat  it  as  a  separate  species  including  forms  with  a  rich 
violet  mycelium.  This  uncertainty  extends  to  the  other  common  species 
of  Rhizoctonia,  so  that  the  European  literature  on  the  subject  offers 
many  difficulties.  Another  fact  which  adds  to  the  confusion  is  that 
both  Rhizoctonia  Solani  and  Rhizoctonia  Crocorum  attack  potato 
stems  and  tubers,  and  while  the  symptoms  caused  by  the  two  fungi  can 
be  easily  distinguished  from  one  another  in  the  field,  it  is  another  mat- 
ter to  differentiate  between  them  in  literature. 

A  partial  list  of  the  hosts  in  Europe  which  are  attacked  by  Rhizoc- 
tonia is  given  below  to  show  the  extent  of  the  distribution  of  this  fun- 
gus. Only  the  more  important  references  are  mentioned. 

Austria  Hungary. — Rhizoctonia  was  first  reported  in  Austria  Hun- 
gary in  1875  on  potato.  Later  7?.  Crocorum  was  found  on  sugar  beet, 
potato  and  lucerne,  and  R.  Solani  (Corticium  vagum),  on  potato. 


1916]  PAKASITIC  RHIZOCTONIAS  IN  AMERICA  307 

Belgium. — R.  Crocorum  has  been  observed  in  Belgium  on  sugar 
beet,  potato,  and  asparagus. 

Denmark. — E.  Rostrup,96'97  during  the  years  1884-1905,  reported 
Rhizoctonia  in  Denmark  on  a  large  number  of  hosts,  including  many 
weeds  and  the  roots  of  several  species  of  forest  trees.  Among  the 
cultivated  crops  mentioned  are  carrot,  clover,  lucerne,  kohl-rabi,  beet, 
turnip,  sugar  beet,  and  potato.  Both  R.  Solani  and  R.  Crocorum 
were  observed  on  the  potato.  In  1892  Rostrup  described  a  new  species 
from  turnip,  which  he  called  Rhizoctonia  fusca  and  which  differed 
only  in  one  or  two  essential  characters  from  R.  Crocorum,  also  found 
on  turnip. 

England. — Rhizoctonia  was  first  reported  in  England  on  mangel 
in  1901,  and  on  potato  in  1904.  The  next  year  Gussow,48  in  an  ex- 
tended account  of  this  disease,  stated  that  it  was  due  to  R.  Solani. 
Salmon,101  in  working  on  a  disease  of  seakale  due  to  R.  Crocorum, 
found  that  it  was  also  able  to  attack  salsify,  parsnip,  carrot,  parsley, 
lettuce,  and  potato. 

Finland. — Reuter91  has  studied  a  Rhizoctonia  in  Finland  which 
causes  a  root  rot  of  rye.  R.  Crocorum  has  been  found  on  beet. 

France. — Between  the  discovery  of  R.  Crocorum  in  France  in 
1728,  on  crocus,  and  1851,  a  number  of  hosts,  including  asparagus, 
bean,  clover,  Citrus,  Coronilla,  grape,  onion,  Rubia,  Sambucus,  and 
tulip,  were  reported. 

Germany. — In  1858  Kiihn04  found  R.  Crocorum  on  sugar  beet  in 
Germany  and  described  the  species  R.  Solani  on  potato  and  carrot. 

Eriksson38  states  that  in  Germany  in  1893  R.  Crocorum  appeared 
on  sugar  beet  in  several  places ;  on  lucerne,  in  55  localities  on  plants 
1  to  5  years  old ;  on  potato,  in  11  localities ;  on  asparagus,  in  3  locali- 
ties ;  on  hop,  in  1  locality ;  and  also  on  a  few  weeds,  such  as  Taraxacum 
officinale,  Convolvulus  arvensis,  etc. ;  and  that  in  1894  it  was  observed 
on  lucerne,  in  77  localities;  on  potato,  in  11  localities;  and  on  red 
clover,  in  8  localities.  The  species  R.  Solani  (Corticium  vagum)  and 
R.  Strobi  Scholtz  on  white  pine,  have  been)  recorded. 

Holland. — Dr.  Johanna  Westerdijk  reports  both  R.  Crocorum  and 
R.  Solani  as  being  very  abundant  on  potato  in  Holland. 

Ireland. — Peihybridge  83'55  has  shown  that  both  R.  Crocorum  and 
R.  Solani  are  present  on  potato  in  Ireland. 

Italy. — R.  Crocorum  has  been  reported  at  various  times  as  present 
on  alfalfa,  sugar  beet,  clover,  asparagus,  carrot,  parsley,  chard,  the 
roots  of  grape,  and  many  weeds  in  Italy.  Rhizoctonia  destruens  Tassi 
occurs  on  the  roots  of  Delphinium. 

Portugal. — The  Rhizoctonia  attacking  sugar  beet  has  been  reported 
from  two  localities  in  Portugal. 

Russia. — R.  Solani  was  reported  on  potato  in  Russia  in  1899. 


308  BULLETIN  No.  189  [June, 

Sweden. — Eriksson37'39  observed  a  disease  of  carrot  and  beet  in 
1898  in  Sweden,  caused  by  R.  Crocorum.  He  was  able  to  inoculate 
this  fungus  on  garden  and  sugar  beet,  alfalfa,  potato,  and  many  weeds 
— Stellaria  media,  Myostis  arvensis,  Galeopsis,  Titraliit,  Erysimum 
clieiranthoides,  Urtica  dioica,  and  Sonchus  sp.  In  addition  to  these 
hosts  Eriksson  has  reported  R.  Solani  (Corticium  vagum)  on  potato 
and  R.  Crocorum  on  turnip  and  kohl-rabi. 

DISTRIBUTION  OF  RHIZOCTONIA  IN  INDIA  AND 
AUSTRALIA 

Shaw,109  working  on  the  morphology  and  parasitism  of  Rhizoctonia 
in  India,  reported  Rhizoctonia  Solani  on  peanut  (Arachis  hypogoea), 
cowpea  (Vigna  catjang),  jute  (Corchorus  capsularis),  Dolichos  Lab- 
lab,  Trichosanthes  cucumernia,  soybean  (Glycine  soja),  mulberry 
(Morus  alba],  sesame,  melon  roots,  cotton,  roots  of  Agave  rigida,  and 
potato. 

In  Australia,  Me  Alpine07  found  R.  Solani  very  widely  distributed 
on  potato. 

PLAN  OF  PROCEDURE 

The  main  object  of  the  present  research  was  to  determine  whether 
of  the  culturable  forms  of  Rhizoctonia  one  or  more  than  one  race  or 
species  is  present  in  this  country.  The  work  was  taken  up  from  the 
following  standpoints : 

1.  Symptoms  of  Khizoctonia  disease  on  various  hosts 

2.  Inoculation  experiments 

3.  Growth  on  media 

4.  Measurement  of  mycelial  cells 

5.  Soil  survey 

SYMPTOMS  OF  RHIZOCTONIA  DISEASE  ON  VARIOUS 

HOSTS 

Following  are  presented  the  observations  of  the  writer  concerning 
the  nature  of  the  diseases  caused  by  Rhizoctonia  on  the  various  hosts, 
together  with  the  principal  facts  which  appear  in  literature  regarding 
Rhizoctonia  on  the  more  important  crop  plants  in  this  country. 

ALFALFA,  Medicago  sativa 

On  March  17,  1914,  the  attention  of  the  author  was  called  to  the 
damping-off  of  young  alfalfa  seedlings  in  the  agronomy  greenhouse 
of  the  Station.  Microscopic  examination  and  pure  cultures  showed  it 
to  be  due  to  Rhizoctonia.  The  seeds  had  been  sown  in  rows  in  pure 
quartz  sand  and  kept  well  moistened.  The  young  seedlings,  on  ger- 
mination, were  somewhat  crowded,  so  that  the  conditions  were  very 


1916]  PARASITIC  EHIZOCTONIAS  IN  AMERICA  309 

favorable  for  damping-off.  The  fungus  could  be  seen  extending  in  all 
directions  over  the  surface  of  the  sand. 

The  fungus  found  on  the  diseased  alfalfa  seedlings  was  compared 
with  a  fungus  obtained  from  mature  alfalfa  plants  sent  from  Iowa. 
Altho  the  mycelium  of  the  two  forms  was  characteristic  of  Rhizoctonia, 
it  differed  in  many  respects,  particularly  in  the  color  of  the  hyphae. 
The  form  on  the  mature  plants  was  undoubtedly  Rhizoctonia  Cro- 
corum,  while  that  on  the  seedlings  was  the  common  Rhizoctonia  Solani. 

Rhizoctonia  was  first  reported  on  the  roots  of  alfalfa  from  Nebraska 
in  1890,  by  Webber,137  as  Rhizoctonia  Medicaginis  DC.  This  fungus 
was  next  mentioned  on  alfalfa  as  Rhizoctonia  violacea,  by  Heald,57 
who  found  it  causing  a  root  rot  in  a  single  locality  in  Nebraska  in 
1906.  In  1908  it  was  reported  by  Freeman,42  under  the  name  Rhizoc- 
tonia violacea,  as  spreading  rapidly  in  the  alfalfa  fields  in  Kansas. 
Freeman  described  the  disease  as  beginning  in  different  parts  of  the 
field  where  at  first  a  single  plant  dies.  From  these  centers  of  infec- 
tion the  fungus  grows  in  all  directions  thru  the  soil,  killing  the  plants 
as  it  proceeds.  Thus  circles  of  steadily  increasing  radii  are  formed,  at 
the  edges  of  which  plants  in  all  stages  of  the  disease  are  found.  The 
great  majority  of  the  plants  within  the  affected  areas  die,  while  those 
which  survive  are  not  vigorous  and  always  lose  their  main  tap  roots. 

The  first  external  sign  of  the  disease  is  a  yellowing  of  the  plant, 
which  soon  after  wilts  and  dies.  The  roots  of  a  dead  or  dying  plant 
are  found  to  be  covered  with  a  violet  or  brownish  red  mat  of  mycelial 
strands,  or  hyphae.  In  a  few  cases  the  tap  root  is  completely  rotted. 
In  less  severely  affected  plants,  the  cortex  of  the  roots  slips  off  easily 
when  the  plants  are  lifted  from  the  soil,  leaving  only  the  central  woody 
cylinder.  This  condition  is  due  to  the  fungous  threads  which  grow 
thru  the  cortex  as  far  as  the  cambium  layer,  which  they  kill.  The 
fungus  forms  sclerotia,  which  may  live  in  the  soil  for  several  years. 

Stewart126  in  1908  mentioned  a  root  rot  and  damping-off  of  alfalfa 
in  the  field  in  New  York.  His  description  of  the  disease  agrees  in 
some  respects  with  the  one  given  by  Freeman.  Later  he  also  noticed 
the  damping-off  of  alfalfa  seedlings  in  the  greenhouse.  He  was  not 
certain  that  Rhizoctonia  Crocorum  was  present  in  New  York,  and  was 
of  the  opinion  that  the  fungus  causing  the  damping-off  of  seedlings 
in  the  greenhouse  was  different  from  the  one  found  in  the  field. 

Heald,58  in  a  later  article  (1911),  described  more  fully  the  disease 
occurring  in  Nebraska.  At  that  time  he  regarded  the  fungus  as  iden- 
tical with  Rhizoctonia  Medicaginis  DC.  of  Europe. 

From  the  above  accounts  it  is  certain  that  there  are  two  species  of 
Rhizoctonia  in  this  country  able  to  attack  alfalfa — R.  Solani,  widely 
distributed,  causing  only  a  damping-off  of  seedlings,  and  R.  Crocorum, 
with  a  limited  distribution,  attacking  as  a  rule  only  mature  plants 
in  the  field.  At  present  this  latter  species  has  been  reported  on  alfalfa 
from  Nebraska,  Kansas,  Iowa,  and  Virginia. 


310  BULLETIN  No.  189  [June, 

ALTERNANTHERA,  Telantliera  sp. 

In  the  fall  of  1912  cuttings  from  alternanthera,  coleus,  and  salvia 
plants  which  had  been  placed  in  the  same  bench  were  found  to  be 
damping-off.  A  microscopic  observation  and  pure  cultures  from  dis- 
eased cuttings  showed  that  RMzoctonia  Solani  was  the  causal  organism. 
Later  the  fungus  was  found  on  alternanthera  plants  in  the  field,  but 
apparently  it  caused  no  injury  there. 

Alternanthera  plants  grow  low  and  bushy,  and  thruout  the  sum- 
mer, no  matter  how  dry  the  season,  the  soil  underneath  is  usually 
moist.  On  close  examination  of  the  tangled  mass  of  branches,  strands 
of  a  fungus,  which  were  later  found  to  be  made  up  of  bundles  of 
hyphae,  could  be  seen  spreading  in  all  directions.  At  first  glance  the 
masses  of  mycelium  looked  very  much  like  old  spider  webs.  A  number 
of  different  varieties  of  alternanthera  were  examined,  and  all  were 
found  to  have  the  characteristic  brown  strands  ramifying  upon  the 
surface  of  the  whole  under  side  of  the  plant.  The  reddish  varieties 
seemed  to  have  more  of  the  fungous  strands  than  did  the  green  and 
variegated  plants.  Cultures  from  the  brown  strands  in  every  case 
yielded  pure  cultures  of  Rhizoctonia  which  corresponded  morphologi- 
cally and  physiologically  to  the  Rhizoctonia  obtained  from  the  cut- 
tings. 

Whether  the  fungus  was  at  any  time  parasitic  on  the  plants  in  the 
field  was  questionable.  However,  cuttings  made  from  them  still  con- 
tained pieces  of  mycelium,  and  when  placed  in  sand  in  the  greenhouse, 
the  fungus  did  parasitize  not  only  the  alternanthera  cuttings  but  others 
as  well. 

The  belief  that  Rhizoctonia  is  present  on  the  branches  of  the  alter- 
nanthera plant  thruout  the  year  was  corroborated  in  1913  and  again 
in  the  fall  of  1914,  when  the  cuttings  made  from  plants  in  the  field 
began  to  damp  off  in  the  cutting  bench.  Repeated  observations  showed 
that  the  fungus  was  present  on  the  plants  in  the  field,  notwithstanding 
the  fact  that  they  had  been  planted  in  new  soil.  Old  plants  brought 
in  from  the  field  were  cut  close  to  the  roots  and  planted  in  flats  in  the 
greenhouse.  These  sprouted  and  developed  new  shoots,  from  which 
cuttings  were  made.  Many  weeds  came  up  in  the  flats  during  the  win- 
ter, and  in  March  both  the  cuttings  and  the  weeds  became  infected 
with  Rhizoctonia.  It  seems,  therefore,  that  the  fungus  is  present  on 
alternanthera  at  all  times  of  the  year,  tho  the  only  injury  it  causes  is 
damping-off  of  cuttings  in  the  greenhouse. 

ALYSSUM,  SWEET,  Alyssum  odoratum 

During  June,  1914,  when  the  bedding  and  decorative  plants  were 
being  set  out  from  the  floricultural  greenhouses  of  the  Station,  about 


1916]  PARASITIC  RHIZOCTONIAS  IN  AMKRICA  311 

twenty-five  plants  of  sweet  alyssum  growing  in  two  and  one-half  inch 
pots  were  found  to  be  diseased.  The  plants  were  tall  and  had  fallen 
over  from  their  own  weight,  so  that  they  formed  a  mat  over  the  pots. 
On  close  examination  the  soil  and  plants  were  found  to  be  covered 
with  the  strands  of  brown  mycelium  which  are  characteristic  of  E. 
Solani.  A  number  of  these  plants  died,  while  on  the  stems  of  others 
the  fungus  formed  small  lesions  near  the  surface  of  the  soil.  The  fun- 
gus continued  to  grow  on  diseased  plants  placed  in  the  field,  and 
killed  a  few  more  of  them. 

AMARANTHUS 

Specimens  of  Rhizoctonia  on  AmarantJius  retroflexus  were  received 
from  Mr.  W.  H.  Burkholder  of  Cornell  University.  The  mycelium  of 
the  Corticium  stage  could  be  easily  recognized  on  the  stems,  while  the 
Rhizoctonia  stage  was  plentiful  on  the  lower  part  of  the  plant.  A  cul- 
ture was  obtained  from  scrapings  made  from  the  mycelium  of  the  Cor- 
ticium stage.  Several  spores  were  found  and  one  basidium  showing 
the  four  sterigmata  was  observed. 

Duggar  and  Stewart32  reported  the  occurrence  of  Rhizoctonia  on 
Amaranfhus  retroflexus  (pigweed)  and  A.  albus  (tumble-weed)  in 
New  York  in  1901.  Several  years  later  Rolfs95  found  the  perfect 
stage,  Corticium  vagum,  in  Florida  on  A.  retroflexus  and  A.  spinosus. 

ASPARAGUS,  ORNAMENTAL,  Asparagus  sprengeri 

Duggar  and  Stewart32  observed  the  effects  of  Rhizoctonia  on  a 
number  of  plants  of  ornamental  asparagus.  They  found  that  the 
plants  were  killed  and  that  many  of  the  leaves  were  bound  to  each 
other  by  the  brown  threads  of  the  Rhizoctonia  hyphge. 

ASTER,  CHINA,  CallistepTius  Jiortensis 

Damping-off  of  aster  seedlings  was  noticed  in  flats  in  the  floricul- 
tural  greenhouses  in  the  spring  of  1913  and  again  in  1914.  The  dis- 
ease first  appeared  as  a  small,  brown  spot  on  one  side  of  the  seedling 
at  the  surface  of  the  soil.  This  lesion  increased  in  size  until  the  seed- 
ling fell  over.  After  a  number  of  seedlings  were  prostrated,  the  fun- 
gus spread  over  them,  and  in  time  a  mat  of  mycelium  covered  the  sur- 
face of  the  soil. 

In  May,  1914,  a  number  of  aster  plants,  four  to  five  inches  high, 
were  planted  in  old  soil  in  which  several  varieties  of  carnation  plants 
had  been  growing  during  the  winter.  There  had  been  more  or  less 
stem  rot  among  these  plants  all  the  season.  After  a  month,  when  the 
aster  plants  were  about  6  inches  high,  they  began  dying  off  and  con- 
tinued to  die  until  they  were  from  9  to  12  inches  high  and  ready  to 


312 


BULLETIN  No.  189 


|  J  tine. 


bud.     Other  aster  plants  set  in  new  soil  at  the  same  time  that  these 
were  transplanted  developed  normally  with  no  stem  rot  whatever. 

TABLE  2. — MORTALITY  .OF  DIFFERENT  VARIETIES  OF  ASTER  GROWN  IN  OLD  CARNA- 
TION SOIL  INFECTED  WITH  Khizoctonia  Solani 


Variety 

Number  of 
plants 

Total 
dead 

Total 
healthy 

Queen  of  the  Market  

50 

1 

49 

Lavender  

50 

1 

49 

Azure  Blue  

50 

4 

46 

Purple  '  

50 

7 

43 

Pure  White  

100 

13 

87 

Shell  Pink  

50 

2 

48 

Eose  Pink  

50 

0 

50 

Deep  Eose  

50 

0 

50 

Crimson  .  . 

50 

1 

49 

As  can  be  seen  from  Table  2,  plants  from  all  but  two  of  the  varie- 
ties died  in  the  bench.  The  varieties  Azure  Blue,  Purple,  and  Pure 
White  were  planted  where  most  of  the  stem  rot  on  the  carnations  oc- 
curred ;  hence  the  higher  number  of  diseased  plants  in  those  varieties 
is  due  to  location  rather  than  to  varietal  susceptibility  to  Rhizoctonia. 

Obviously  the  Rhizoctonia  causing  carnation  stem  rot  was  in  this 
case  able  to  attack  healthy  aster  plants.  The  stem  rot  of  these  plants 
was  typical  and  very  similar  to  the  rot  of  carnations.  The  first  sign 
of  the  disease  was  a  yellowing  and  drooping  of  the  foliage,  followed, 
sooner  or  later,  depending  on  weather  conditions,  by  a  sudden  wilt- 
ing of  the  whole  plant.  When  the  plant  was  pulled,  the  bark  of  the 
stem  near  the  surface  of  the  soil  would  slough  off,  leaving  only  the  dis- 
colored woody  tissues. 

A  stem  rot  of  aster  due  to  Rhizoctonia  has  been  reported  only  once 
before  in  this  country.  Duggar  and  Stewart32  in  1901  found  the  my- 
celium in  the  tissues  of  aster  and  later  isolated  a  pure  culture  from 
them.  They  observed  the  disease  in  a  number  of  localities  in  New 
York  during  that  summer. 

BEAN,  Phaseoliis  vulgaris 

The  damping-off  of  young  bean  seedlings  by  R.  Solani,  which 
has  been  observed  in  the  greenhouse  and  in  the  field,  is  characterized 
by  the  production  of  small  lesions  at  the  surface  of  the  ground  either 
on  one  side  of  the  stem  or  girdling  it,  followed  by  the  falling  over  and 
death  of  the  seedling. 

When  the  fungus  attacks  older  bean  plants,  lesions  of  various 
sizes  are  produced  just  below  the  surface  of  the  ground,  at  the  surface, 
or  one  or  two  inches  above  it.  In  some  plants  these  discolored  spots 
can  be  found  on  the  larger  roots  also.  The  lesions,  as  a  rule,  have  a 


1916} 


PARASITIC  EHIZOCTONIAS  IN  AMERICA 


313 


FIG.  8. — STEMS  OP  MATURE  BEAN  PLANTS  WHICH  HAD  BEEN  PLACED  IN  A  BENCH 
IXFECTED  WITH  Ehizoctonia  Solani  ORIGINALLY  OBTAINED  FROM 
CARNATION  PLANTS 

reddish  brown  band  with  a  lighter  colored,  sunken  area,  and  extend 
thru  the  cortical  layer  into  the  woody  tissues.  As  on  the  young  seed- 
lings, the  spots  are  usually  localized  on  one  side  of  the  stem,  but  in 
some  cases  one  lesion  may  girdle  the  plant.  These  lesions  weaken  the 
stem  and  cause  it  to  break  off  easily. 

The  first  account  of  Ehizoctonia  causing  a  disease  of  bean  was  given 
by  Atkinson.4  He  reported  that  during  the  winter  of  1894-95  it 
caused  damping-off  of  bean  seedlings  and  attacked  plants  that  were 
from  6  to  10  inches  high.  He  referred  to  this  form  as  "the  sterile 
fungus,"  and  stated  that  its  most  characteristic  peculiarity  was  the 
mode  of  branching. 

In  1901  Duggar  and  Stewart32  reported  this  fungus,  from  New 
York,  as  the  cause  of  a  stem-rot  disease  of  red  kidney  beans  in  the  field 
and  of  a  damping-off  among  seedling  beans  in  the  greenhouse. 


314  BULLETIN  No.  189  [June, 

In  190-1:  Hedgcock60  reported  as  follows: 

"The  bean  crop  in  the  vicinity  of  St.  Louis  was  severely  injured  by  a  Khi- 
zoctonia  which  attacked  the  stems  and  large  roots  of  the  plant  and  also  produced 
brown  sunken  areas  on  the  surface  of  the  pods,  penetrating  the  latter  and  discolor- 
ing the  seeds.  An  examination  of  a  number  of  seeds  whose  surface  was  discolored, 
disclosed  the  fact  that  the  mycelium  of  the  fungus  had  established  itself  in  the 
second  coat  and  in  many  instances  had  formed  minute  sclerotia  there  without  rot- 
ting the  seed  or  even  penetrating  the  cotyledons.  The  presence  of  the  fungus  did 
not  prevent  the  germination  of  the  seed. ' ' 

Fulton44  in  1908  showed  that  Rhizoctonia  from  infected  pods 
caused  damping-off  of  seedling  beans  and  of  month-old  plants. 

A  serious  outbreak  of  the  stem  rot  of  beans  was  reported  from  New 
York  by  Barrus9  in  1910.  He  found  that  in  some  fields  as  many  as 
30  percent  of  the  plants  were  infected.  In  the  same  fields  during  the 
following  season  it  caused  the,  death  of  at  least  5  to  6  percent  of  the 
seedlings ;  later  in  the  season,  after  a  rainy  spell,  a  large  percentage 
of  the  pods  in  contact  with  the  ground  became  infected. 

BEET,  Beta  vulgaris 

Young  seedlings  of  the  garden  beet,  in  flats,  were  found  damping 
off  in  the  vegetable-gardening  greenhouses  of  the  Station,  July  10, 
1913.  Cultures  showed  that  R.  Solani  was  the  sole  cause  of  the  dis- 
ease. Characteristic  lesions  were  found  on  the  beets  at  the  surface  of 
the  ground,  and  strands  of  mycelium  could  be  plainly  seen  spreading 
out  on  the  surface  of  the  soil. 

As  with  root  rot  of  other  fleshy  crops,  the  fungus  gains  its  first 
held  at  the  crown  of  the  mature  plant,  which,  as  a  rule,  is  just  below 
the  surface  of  the  ground.  The  first  evidence  of  the  disease  is  a 
darkening  of  the  leaf  bases,  followed  by  the  rotting  of  the  crown. 
The  leaves  retain  their  color  for  a  long  time,  or  until  the  leaf  stalks 
rot  off  almost  completely.  With  the  rotting  at  the  crown,  the  beets 
begin  to  crack  from  this  point.  While  the  tissues  around  the  cracks 
remain  firm,  as  a  rule,  for  a  long  time,  the  crown  is  usually  soft,  a 
condition  due  to  the  entrance  of  other  organisms.  Lesions  are  some- 
times formed  on  the  sides  of  the  beets,  often  extending  deep  into_  the 
tissues.  When  weather  conditions  become  unfavorable  to  the  fungus, 
the  rotting  and  cracking  stops  and  the  plant  may  recover  from  the 
attack.  The  disease  is  generally  scattered  thru  the  field,  only  a  few 
plants  in  a  given  area  being  affected. 

Under  the  name  Rhizoctonia  beta?  Kiihn,  Pammel70  in  1891  de- 
scribed a  root  rot  of  sugar  beets.  He  was  the  first  investigator  to  re- 
port serious  damage  caused  by  Rhizoctonia  in  this  country.  Duggar28 
in  1899  regarded  the  root-rot  disease  of  sugar  beet  due  to  Rhizoctonia 
as  one  of  the  important  diseases  of  that  plant.  At  the  present  time 
this  disease  is  very  widespread  and  is  the  cause  of  considerable  loss, 
especially  in  irrigated  regions. 


1916] 


PARASITIC  UHIZOCTONIAS  TN  AMERICA 


315 


FIG.  9. — GARDEN   BEET  INOCULATED  WITH  ' Bhizoctonia  Solani  FROM   CARNATION, 
SHOWING  A  LATE  STAGE  OP  INFECTION  (Experiment  8) 

Damping-off  of  sugar-beet  seedlings  has  been  reported  by  Selby,108 
from  Ohio,  and  by  Smith,113  from  California. 

BEGONIA 

Mr.  H.  W.  Anderson  in  1911  found  a  number  of  begonia  cuttings  in 
the  floricultural  greenhouses  that  were  damping  off  badly  because  of 
Rhizoctonia  infection.  The  symptoms  were  similar  to  those  described 
for  cuttings  of  alternanthera. 

Damping-off  of  begonia  cuttings  has  also  been  observed  in  New 
York  by  Duggar  and  Stewart,32  and  in  North  Carolina  by  Stevens  and 
Wilson.122 

BLACKBERRY,  Eubus  sp. 

Root  disease  of  blackberry  and  raspberry  caused  by  Rhizoctonia 
has  been  reported  only  once  in  this  country.  Paddock  7r>  of  Colorado, 
who  studied  this  disease,  described  it  as  follows : 

' '  The  trouble  was  first  noticed  by  the  foliage  becoming  light  green  or  yellow- 
ish. Later  in  the  season  leaves  on  occasional  plants  began  to  curl  and  shrivel  as 
parts  of  the  plant  below  ground  were  attacked,  but  the  greatest  injury  occurred  on 
the  canes  above  the  crown.  Here  the  bark  was  discolored  and  shrunken  from  the 
crown  to  the  surface  of  the  soil,  or  a  short  distance  above.  The  fungus  grew  out 
within  the  bark,  destroying  the  tissues,  and  interfering  with  the  movements  of 
plant  food.  The  injury  commonly  extended  around  the  cane,  and  when  it  became 
deep  enough  to  cut  off  the  supply  of  moisture  and  food,  the  plant  died. ' ' 

BUCKWHEAT,  Fagopyrum  esculentum 

In  1911  Stevens  and  Wilson120'121  mentioned  a  serious  outbreak  of 
Rhizoctonia  on  buckwheat  in  the  western  part  of  North  Carolina.  No 
description  of  the  disease  was  given. 


316 


BULLETIN  No.  189 


[June, 


CABBAGE,  Brassica  oleracea 

Atkinson,4  in  1895,  in  his  article  on  damping-off  diseases,  men- 
tioned cabbage  seedlings  as  being  susceptible  to  damping-off  by  Rhi- 
zoctonia. 

Duggar  and  Stewart32  in  1898  received  from  Illinois  specimens 
of  cabbage  seedlings  which  had  been  diseased  by  Rhizoctonia.  They 
found  that  the  disease  sometimes  affected  very  young  seedlings,  caus- 
ing damping-off,  but  that  it  was  more  common  after  the  plants  had 
developed  one  or  two  true  leaves.  In  the  latter  instances,  small  lesions 
at  or  below  the  surface  of  the  soil  characterized  the  disease.  Later, 
Duggar  and  Stewart  found 
Rhizoctonia  causing  a  sim- 
ilar disease  of  cauliflower 
seedlings  in  New  York. 
The  plants  showed  ulcera- 
tion  at  the  bases  of  the 
stems,  the  entire  cortex  in 
some  cases  having  disap- 
peared. 

Fawcett40  reported  a 
stem  rot  of  cabbage  seed- 
lings due  to  Corticium  va- 
gum  B.  &  C.,  in  Florida,  in 
1909.  According  to  his 
description,  the  disease 
was  a  typical  stem  rot, 
with  a  softening  of  the  epi- 
dermis followed  by  a  shriv- 


FIG.  10. — STEMS  OF  YOUNG 
CABBAGE  PLANTS  INOCU- 
LATED WITH  Rhizoctonia 
Solani  FROM  CARNATION 


FIG.  11. — STEM  OF  AN  OLD  CABBAGE 
PLANT  WHICH  HAD  BEEN  PLACED  IN 
A  BENCH  INFECTED  WITH  Ehizoc- 
tonia  Solani  FROM  CARNATION  (Ex- 
periment 9) 


PARASITIC  RHIZOCTONJAS  IN  AMERICA  317 

eliiip  of  the  outside  tissues  and  a  browning  of  the  leaves.  However, 
the  plants  so  affected  did  not  wilt  down  entirely,  and  many  of  them 
recovered. 

CANDYTUFT,  Iberis  sp. 

During  June,  1914,  a  few  plants  of  candytuft  that  had  been  grow- 
ing in  three-inch  pots  in  the  floricultural  greenhouses,  rotted  off  at  the 
surface  of  the  ground.  The  symptoms  were  similar  to  those  described 
for  sweet  alyssum.  Microscopic  examination  of  diseased  tissue  re- 
vealed R.  Solani  in  every  case.  Dense  masses  of  hyphse  covering  the 
leaves  and  stems  of  these  plants  were  plainly  visible. 

Duggar  and  Stewart32  in  1901  reported  damping-off  by  Rhizoctonia 
of  cuttings  of  candytuft  in  New  York. 

CARNATION,  Dianihus  caryophyllus 

Rliizoctonia  Solani  attacks  carnation  plants  of  all  ages,  both  in  the 
field  and  in  the  greenhouse,  causing  not  only  stem  rot,  but  damping- 
off  of  cuttings,  of  which  it  is  one  of  the  principal  causes. 

The  symptoms  of  stem  rot  of  carnation  are  very  characteristic  of 
the  effects  of  R.  Solani  (Fig.  1).  The  fungus  usually  attacks  the 
stem  of  the  plant  at  the  surface  of  the  ground  or  occasionally  just 
above  or  below.  As  a  rule,  the  first  indication  of  the  disease  is  a  pale 
green  color  of  an  entire  plant  or  of  a  single  branch.  This  lighter  color 
can  be  noticed  in  most  cases  for  several  days  before  the  actual  wilting 
takes  place.  During  cloudy  weather  the  plant  does  not  wilt  for  two 
weeks  and  sometimes  for  even  longer,  altho  the  stem  may  be  almost 
completely  rotted ;  in  sunny  weather  wilting  occurs  much  sooner. 

If  the  stem  of  a  plant  that  shows  the  first  sign  of  wilting  is  pressed 
just  at  the  surface  of  the  soil,  a  soft  place  is  felt  and  a  slight  twist  is 
sufficient  to  slough  off  the  bark.  Beneath  this  is  a  slimy,  wet  area, 
which  gives  this  rot  its  characteristic  name.  Sometimes,  however,  the 
stem  is  dry  at  the  point  of  attack,  and  upon  being  broken  off,  the  fibers 
appear  to  be  separated  and  stringy. 

The  fungus  enters  the  cracks  in  the  corky  layer  of  the  bark  and  at- 
tacks the  cambium  layer,  causing  the  sloughing  off  of  the  bark.  It 
then  penetrates  the  woody  tissues,  and  can  be  found  even  in  the  pith. 
The  plant  may  remain  alive  after  the  cambium  layer  is  destroyed  until 
the  fungus  plugs  the  vessels.  If  a  diseased  plant  is  left  in  the  soil  for 
some  time,  the  mycelium  overruns  the  stem,  and  dark,  round  sclerotia 
are  formed  either  directly  on  the  bark  or  in  the  crevices,  or  cracks. 

The  Rhizoctonia  disease  of  carnation  has  been  known  to  florists 
ever  since  carnations  have  been  grown  as  a  commercial  crop  in  the 
greenhouse.  In  Volume  I  of  the  American  Florist,  1886,  is  found  the 
following  paragraph,  \vhich  is  probably  the  first  published  statement 
concerning  the  stem  rot  of  carnation  in  this  country. 

"  In  a  few  days  plants  began  to  show  signs  of  wilting,  and  upon  examination 
I  found  them  rotted  off  just  at  the  top  of  the  ground,  tho  half  an  inch  under 
the  ground  the  stems  appeared  perfectly  healthy. ' ' 


318 


BULLETIN   NO.  189 


[June, 


1916]  PARASITIC  RHIZOCTOXIAS  IN  AMERICA  319 

While  the  cause  of  the  disease  was  not  known  at  that  time,  from 
the  description  of  the  symptoms  it  is  not  to  be  doubted  that  it  was  due 
to  Rhizoctonia. 

A  great  loss  of  plants  from  stem  rot  occurred  thruout  the  country 
about  1900.  Below  are  given  a  few  excerpts  from  notes  on  this  dis- 
ease which  have  appeared  during  the  last  thirty  years,  some  of  which 
agree  with  our  present-day  ideas: 

1886.     "Deep  planting  causes  the  disease  in  many  houses." 

' '  In  our  opinion  high  temperature  and  deep  planting  have  much  to  do  with 
the  disease. ' ' 

1898.  ' '  The  most  dangerous  disease  that  attacks  the  carnation.  Some  varie- 
ties appear  more  subject  to  this  disease  than  others,  and  there  is  considerable 
complaint  about  Flora  Hill  and  Silver  Spray  this  season.  The  most  common 
error  that  very  often  leads  to  this  disease  is  too  deep  planting.  The  plants  should 
never  be  planted  deeper  than  they  stood  in  the  field,  preferably  not  so  deep.  The 
stem  of  the  plant  should  be  out  of  the  ground  sufficiently  to  hold  the  branches 
away  from  the  soil.  I  believe  this  disease  is  not  found  on  carnations  alone,  but 
on  other  plants  too,  and  the  spores  of  this  fungus  may  have  been  embedded  in  the 
soiP,  carried  over  or  imprisoned,  dormant  in  the  plant  from  the  cutting  bench. 

' '  To  check  and  prevent  the  spreading  of  this  disease,  dust  flour  of  sulfur 
over  the  plants,  and  shake  them  so  it  will  lodge  on  the  stem  and  branches  and  on 
the  soil  around  the  stem. ' ' 

1900.  "Climatic  conditions  rather  than  anything  else  are  the  chief  causes  of 
the  trouble.  High  ranges  of  temperature  whether  in  the  cutting  bench,  field,  or 
house,  the  results  are  the  same,  the  amount  of  rot  varying  with  preceding  condi- 
tions. Thus,  after  heavy  rains  inducing  soft  growth,  a  rise  of  temperature  into 
the  90 's  is  a  capital  condition  for  the  development  of  stem  rot.  Some  varieties 
are  also  more  susceptible  to  attacks  than  others,  the  woodier  ones  being  able  to 
withstand  it  more  than  those  of  soft  growth. ' ' 

1904.     ' '  Stem  rot  is  due  to  allowing  plants  to  become  pot-bound. 

' '  Rich  soil  with  too  much  manure  causing  a  rapid  growth  causes  stem  rot. 
I  believe  this  to  be  responsible  for  more  stem  rot  than  all  other  conditions  com- 
bined. Too  deep  planting  also  favorable  for  stem  rot.  Water  when  absolutely 
necessary  and  then  water  thoroly. ' ' 

1906.  "Presence  of  wounds   on   the   bark,   or  punctures  made   by   insects; 
faulty  planting;  sour  or  too  highly  enriched  soil;  lack  of  drainage;  careless  cul- 
tivation;  lack  of  fresh  circulating  air;   the  maintenance  of  too  great  heat  com- 
bined with  atmosphere  heavily  charged  with  stagnant  moisture  during  the  time 
when  the  outdoor  stocks  are  housed,  will  cause  stem  rot  to  become  severe  in  the 
benches. ' ' 

1907.  ' '  Stem  rot  is  the  most  dreaded  and  only  disease  of  carnations  in  the 
South. ' ' 

1909.     "Stem  rot  more  dreaded  in  South  than  in  North." 

1911.  "Fresh  air,  plenty  of  circulation,  a  sweet  soil,  and  proper  watering 
will  avoid  to  a  great  extent  the  appearance  of  stem  rot  or  stop  its  spread.  Weather 
conditions  seem  to  play  an  important  part,  and  in  most  cases  as  soon  as  cold 
nights  are  the  rule,  our  troubles  grow  less.  The  greatest  benefit  is  derived  thru 
a  clear  and  rather  dry  atmosphere.  Deep  planting  not  so  important.  Too  much 
manure  not  necessarily  a  cause  of  stem  rot. 

"Stem  rot  is  more  prevalent  in  sour  soils  than  others.  The  surface  of  the 
soil  should  be  kept  open  by  frequent  scratching.  A  dry  interior  and  a  wet  surface 
is  very  conducive  to  stem  rot. ' ' 

1913.     "Stem  rot  in  the  South  is  more  serious  than  in  the  North." 

The  following  older  carnation  varieties  have  beeen  reported  as  being 
especially  susceptible  to  stem  rot :  La  Purite,  Crimson  King,  De  Graws, 
Sewan.  Flora  Hill,  Silver  Spray,  McGowan,  Portias,  Scott,  Jubilee, 


320  BULLETIN  No.  189  [June, 

Craig,  Boston  Market,  Crane,  Lawson,  Lady  Bountiful,  Winsor.  Sev- 
eral of  these  varieties  are  still  propagated  by  a  few  growers  and  with 
good  success,  but  the  majority  of  them  have  been  discarded.  Of  the 
newer  types  no  one  seems  to  be  more  susceptible  than  the  others. 

To  Duggar  and  Stewart30  is  owed  the  discovery  that  Rhizoctonia 
is  the  cause  of  stem  rot  of  carnation.  This  they  proved  conclusively 
in  1899  by  inoculation  experiments  with  pure  cultures,  repeated  many 
times.  Duggar  and  Stewart  state  that  this  stem  rot  is  one  of  the  most 
troublesome  of  the  carnation  diseases  and  probably  occurs  thruout  the 
United  States  wherever  the  carnation  is  grown.  Stewart123'124  at  the 
same  time  distinguished  between  two  distinct  diseases,  both  called 
' '  stem  rot. ' '  One  is  caused  by  Rhizoctonia,  and  the  other  by  Fusarium. 

Card  and  Adams13  of  Rhode  Island  studied  methods  of  control  of 
both  Fusarium  and  Rhizoctonia  rots.  They  came  to  the  conclusion 
that  the  use  of  clean,  fresh  sand  in  the  cutting  bench  helps  to  control 
the  fungus.  They  also  found  that  stable  manure  does  not  favor,  the 
spread  of  the  disease. 

In  1902  Stone  and  Smith129  reported  carnation  stem  rot  in  Massa- 
chusetts. Two  years  later  Clinton14  reported  the  presence  of  the 
disease  in  Connecticut.  In  1906  Heald57  stated  that  it  was  found  in 
the  field  and  in  the  greenhouse  near  Lincoln,  Nebraska.  Blake  and 
Farley10  in  New  Jersey  conducted  a  number  of  soil  experiments  for 
the  control  of  stem  rot. 

CARROT,. Daucus  carota 

Occasionally  R.  Solani  causes  damping-off  of  carrot  seedlings, 
but  the  plants  seem  to  be  more  susceptible  later,  when  the  fleshy  root 
is  formed.  Here  the  rot  starts  at  the  crown  and  works  up  into  the  leaf 
bases.  It  also  progresses  into  the  interior  of  the  fleshy  root,  as  a  rule 
showing  no  signs  on  the  exterior  for  some  time.  In  some  cases  lesions 
are  found  on  the  exterior  of  the  carrot  and  on  the  larger  secondary 
roots  where  they  branch  from  the  fleshy  part. 

Duggar  and  Stewart32  were  the  first  to  find  a  disease  of  carrot  due 
to  Rhizoctonia.  In  1911  Heald  and  Wolf59  reported  from  Texas  the 
Corticium  stage  of  the  fungus  on  carrot.  They  stated  that  the  roots 
were  covered  by  white,  ropy  strands  of  the  fungus,  but  that  no  serious 
rotting  was  observed. 

CELERY,  Apium  graveolens 

A  damping-off  of  celery  seedlings  in  flats  by  RMzoctonia  Solani  has 
been  observed  in  the  Station  vegetable-gardening  greenhouses.  The 
symptoms  are  similar  to  those  described  for  beets. 

During  a  search  in  the  market  in  the  winter  of  1914  for  leaf  spot 
and  soft  rot  on  celery,  several  bunches  shipped  from  New  York  were 


1916]  PARASITIC  BHIZOCTONIAS  IN  AMERICA  321 

found  to  have  a  brown  mycelium  and  many  small  sclerotia  between  the 
stalks  near  the  base.  The  fungus  was  causing  no  injury  to  the  celery. 
When  examined  in  the  laboratory,  the  mycelium  and  sclerotia  proved 
to  be  those  of  Rhizoctonia.  Pure  cultures  of  the  fungus  were  obtained 
readily  from  the  sclerotia.  Repeated  examinations  of  new  shipments 
of  celery  from  New  York  showed  that  in  the  majority  of  cases  Rhizoc- 
tonia was  present  between  the  stalks. 

Duggar  and  Stewart32  in  1901  were  the  first  to  report  Rhizoctonia 
causing  a  destructive  damping-off  of  celery  seedlings.  Rolfs95  in  1905 
reported  a  damping-off  of  seedlings  in  Florida  caused  by  Corticium 
vagum  B.  &  C.  Van  Hook136  found  a  Rhizoctonia  associated  with  a 
root  rot  of  celery  in  the  field.  He  did  not  believe,  however,  that  this 
fungus  was  the  cause  of  all  the  trouble.  Affected  plants  never  attained 
full  size,  and  an  examination  of  the  roots  showed  considerable  decay. 
The  disease  seemed  to  affect  the  main  roots,  which  rotted  off  rapidly 
near  the  crown.  The  fact  that  seed  beds  in  new  soil  did  not  entirely 
control  the  trouble  showed  that  the  fungus  Rhizoctonia  was  present  in 
the  new  soil,  tho  not  in  any  great  amounts.  Halligan,51  in  Michigan, 
has  also  studied  the  damping-off  of  celery  plants  in  the  seed  bed. 

Centaurea  gymnocarpa 

In  the  spring  of  1914  a  large  number  of  seedlings  of  Centaurea 
gymnocarpa,  including  some  of  those  which  were  potted,  damped  off. 
By  June  many  of  the  potted  plants  were  dying  with  stem  rot,  the  dis- 
ease having  been  carried  over  on  affected  seedlings  and  in  a  few  cases, 
no  doubt,  on  healthy  ones.  Microscopic  examination  and  pure  cultures 
showed  that  in  each  case  R.  Solani  was  present  in  the  diseased  tissues. 
The  progress  of  the  disease  was  rather  typical.  The  first  symptom 
was  the  wilting  and  drying  up  of  the  foliage.  On  pulling  up  the 
plant,  a  number  of  the  leaves  were  seen  to  be  rotted  off  at  the  crown, 
while  the  bark  on  the  stem  below  the  surface  of  the  ground  sloughed 
off  and  the  tissues  beneath  were  wet  and  stringy. 

CLOVER,  RED,  Trifolium  pratense 

In  the  spring  of  1914  damping-off  of  red  and  Japanese  clover  was 
observed  in  the  agronomy  greenhouses.  A  culture  easily  obtained 
from  the  fungus  appeared  to  be  the  same  in  all  respects  as  the  one 
isolated  from  alfalfa  seedlings  which  were  growing  under  similar  con- 
ditions in  close  proximity. 

Stevens  and  Wilson  122  in  1911  reported  that  in  a  field  of  clover  in 
North  Carolina  the  roots  were  being  attacked  by  Rhizoctonia  and  were 
suffering  some  damage.  This  is  the  only  instance  in  which  Rhizoctonia 
has  been  reported  as  injuring  clover  in  the  field. 


322  BULLETIN  No.  189  [June, 

COLEUS,  Coleus  sp. 

In  November,  1912,  cuttings  of  coleus  began  to  damp  off  in  a  bench 
in  the  floricultural  greenhouses.  The  variegated  green  varieties  seemed 
more  susceptible  to  the  fungus  than  the  variegated  red  and  yellow.  The 
trouble  was  found  to  be  due  to  R.  Solani.  The  infected  cuttings  showed 
characteristic  lesions  on  the  stems  at  the  surface  of  the  sand.  These 
lesions  were  quite  large  and  distinct,  brown  in  color,  and  depressed 
several  millimeters  at  the  center.  They  were  generally  found  on  one 
side,  but  in  some  cases  the  whole  cutting  was  girdled.  Practically  all 
the  coleus  cuttings  in  the  bench  damped  off  in  this  manner. 

During  October,  1913,  Ehizoctonia  was  found  causing  a  damping- 
off  of  coleus  seedlings  planted  very  close  in  flats.  About  half  the  plants 
damped  off. 

Duggar  and  Stewart32  reported  a  damping-off  of  coleus  cuttings 
in  New  York,  caused  by  Rhizoctonia,  similar  to  that  observed  at  this 
Station. 

CONIFEROUS  SEEDLINGS 

The  first  case  reported  of  damping-off  of  white-pine  seedlings  due 
to  Rhizoctonia  was  by  Duggar  and  Stewart,32  from  New  York.  Ten 
years  later  Clinton1 7  mentioned  the  damping-off  of  a  number  of  conif- 
erous seedlings. 

Hartley,55  who  made  a  study  of  the  damping-off  of  coniferous  seed- 
lings in  the  West,  found  that  Rhizoctonia  is  one  of  several  organisms 
involved.  He  wrote  as  follows : 

"Ehizoctonia  (probably  Corticium  vagum  B.  &  C.),  which  causes  dumping-off 
of  very  young  seedlings,  sometimes  continues  to  work  in  patches  till  the  plants  are 
two  months  old  or  even  more.  On  sandy  soil,  when  seedlings  from  five  to  nine 
weeks  old  are  killed,  the  youngest  and  deepest  parts  of  the  roots  are  usually  first 
attacked.  At  Halsey,  roots  of  Eocky  Mountain  yellow-pine  seedlings  about  seven 
weeks  old  have  been  attacked  at  points  as  much  as  eleven  inches  below  the  ground 
surface.  In  many  plants  as  old  as  this  the  older  parts  of  the  roots  resist  the  en- 
trance of  the  fungus  which  has  rotted  the  younger  parts  and  throw  out  new  root 
branches,  so  that  recovery  takes  place  without  any  evidence  of  the  damage  being 
shown  by  the  plant  above  ground. ' ' 

Coreopsis  lanceolata 

Duggar  and  Stewart32  in  1901  mentioned  the  fact  that  next  to  a 
plot  of  sweet  williams  that  were  being  killed  by  Rhizoctonia,  were  two 
rows  of  Coreopsis  lanceolata  which  were  also  diseased.  They  stated 
that  "only  a  few  plants  were  killed,  but  from  many  of  them  the  lower 
leaves  had  rotted  away.  The  rot  seemed  to  start  in  the  base  of  the 
petiole,  where  it  came  in  contact  with  the  soil.  The  decaying  leaves 
were  overrun  with  Rhizoctonia." 


1'AKAsiTK'  BHIZOCTOMIAS  IN  AMERICA 


323 


CORN,'  Zea  mays 

In  1914,  during  the  progress  of  the  soil  survey  for  R.  Solani,  the 
fungus  was  found  frequently  on  corn  roots  in  the  field.  It  could  not 
be  determined  whether  the  fungus  penetrated  the  roots  or  not,  but 
there  was  no  question  as  to  the  abundance  of  the  mycelium  on  the 
roots. 

Rolfs05  in  1905  reported  Corticium  vagum  B.  &  C.  on  corn  in 
Florida. 

COTTON,  Gossypium  herbacsum 


Grlover40  in  1855  described  a 
respects  is  the  same  as  the  disease 


FIG.  13. — STEMS  OF  YOUNG  CARNA- 
TION PLANTS  INOCULATED  WITH 
EHIZOCTONIA  FROM  COTTON, 
SHOWING  LESIONS  CHARACTERIS- 
TIC OF  SORE  SHIN  OF  COTTON 
CAUSED  BY  THE  SAME  FUNGUS 


sore  shin  of  cotton,  which  in  some 
of  seedling  cotton  caused  by  Rhizoc- 
tonia.  He  stated  that ' '  the  cause  is 
attributed  by  many  to  cold,  cutting 
winds,  when  the  plant  is  very 
young.  Others,  however,  assert  that 
when  a  high  wind  shakes  a  tender 
plant,  the  main  stem  is  so  much 
bent  and  twisted  that  the  sap  ves- 
sels are  upturned  and  a  serious  in- 
jury occurs." 

One  of  the  causes  of  sore-shin 
disease  of  cotton  remained  undis- 
covered until  Atkinson,5  in  1896, 
found  in  the  diseased  tissues  a  ster- 
ile mycelium,  which  he  later  identi- 
fied as  Rhizoctonia.  By  means  of 
pure-culture  methods  and  inocula- 
tion experiments  he  further  proved 
that  this  sterile  fungus  was  the 
cause  of  sore  shin  and  also  of  seed- 
ling rot  and  damping-off  of  cotton. 
He  describes  the  Rhizoctonia  dis- 
ease of  cotton  as  follows : 


' '  There  are  several  phases  of  the  disease.  Sometimes  the  tissues  undergo  a 
soft  rot  which  progresses  very  rapidly,  and  the  early  stages  are  not  marked  by  any 
striking  color  characteristics.  Another  phase  may  progress  rapidly  or  slowly  and 
is  usually  quite  well  characterized  by  a  reddish  brown  color  which  accompanies  it. 
This  phase  is  also  characteristic  in  that  it  is  usually  manifested  on  one  side  of 
the  stem  in  the  form  of  an  ulcer  which  gradually  deepens  until  the  vascular  sys- 
tem is  reached,  when  the  life  of  the  plant  becomes  really  endangered.  Even  when 
this  stage  is  reached,  however,  the  plant  may,  and  does  frequently,  recover. 

"This  latter  phase  is  characteristic  of  a  very  common  disease  of  seedling 
cotton.  It  is  called  by  the  planters  in  many  places  '  sore  shin. ' 

"The  diseased  portion  of  the  plant  is  just  beneath  the  surface  of  the  ground 
and  presents  an  area  of  shrunken  tissue  of  a  dull  brown  or  reddish  color.  The 


324  BULLETIN  No.  189  [June, 

size  of  the  shrunken  area  and  the  depth  of  the  injury  are  proportionate  to  the 
serious  condition  of  the  ulcer,  as  it  may  be  termed.  If  the  injury  remains  con- 
fined to  the  superficial  tissues,  the  plant  will  usually  recover.  It  does  sometimes 
recover  when  the  injury  reaches  the  vascular  tissue,  but  more  frequently  death 
results  when  the  trouble  has  progressed  thus  far. ' ' 

No  further  original  work  has  been  done  on  this  disease  since  the 
time  of  Atkinson,  altho  several  of  the  southern  experiment  stations 
have  published  bulletins  on  cotton  diseases,  including  the  sore  shin 
and  seedling  rot  due  to  Rhizoctonia. 

DiantJius 

R.  Solani  was  isolated  from  diseased  plants  of  DiantJius  barbatus 
(Newport  Pink),  during  July,  1913,  in  the  perennial  garden  of  the 
Station.  This  variety  and  DiawtJius  barbatus  (single  mixed)  were 
much  more  susceptible  to  stem  rot  than  were  any  of  the  other  varieties 
grown.  In  fact,  practically  every  plant  of  these  two  varieties  died 
from  stem  rot  during  the  summer.  These  varieties  are  more  like  the 
carnation  than  any  of  the  others,  and  when  affected,  the  symptoms  of 
the  disease  were  very  similar  to  those  of  stem  rot  of  carnation.  The 
first  evidence  of  the  disease  was  the  pale  green  color  of  the  leaves, 
followed  in  many  cases  by  a  sudden  wilting  of  the  foliage.  When 
plants  in  this  stage  were  pulled  up,  the  bark  readily  sloughed  off, 
leaving  the  wood  exposed.  When  plants  in  the  later  stages  of  the 
disease  were  pulled  up,  the  stem  usually  broke  off  at  the  surface  of  the 
ground,  exposing  stringy  tissue. 

During  the  same  month,  a  disease  of  DiantJius  sequeri  and  D. 
plumarius  was  under  observation.  Diseased  parts  of  these  plants 
yielded  Rhizoctonia  in  every  instance.  In  the  case  of  D.  sequeri  the 
fungus  seemed  to  be  living  saprophytically  among  the  numerous  pros- 
trate, bushy  branches.  The  brown  strands  of  the  mycelium  could  be 
plainly  seen  running  thru  the  bushy  mass  of  the  plant.  Only  a  few 
plants  died.  Unlike  the  case  of  D.  barbatus,  there  was  no  characteris- 
tic sloughing  off  of  the  bark,  but  a  more  or  less  general  rotting  of  the 
whole  stem,  which  left  the  tissues  very  dry  and  stringy.  The  attack 
was  not  confined  to  the  main  stem,  but  affected  any  of  the  branches 
which  touched  the  ground. 

Most  of  the  plants  of  D.  plumarius,  occupying  a  space  about  three 
feet  long,  died  from  attacks  of  the  fungus.  The  symptoms  of  the  dis- 
ease were  very  similar  to  those  of  D.  sequeri,  the  rotting  appearing 
to  extend  gradually  from  one  point  thru  the  whole  stem.  As  with  D. 
sequeri  also,  the  bushy  habit  of  the  plant  gave  ample  protection  to  the 
fungus,  and  the  radiating  strands  of  the  brown  mycelium  of  Rhizoc- 
tonia were  visible  to  the  naked  eye. 

Duggar  and  Stewart32  in  1900  found  a  badly  diseased  plot  of 
DiantJius  barbatus  in  which  90  percent  of  the  plants,  in  the  course 
of  the  season,  died  from  stem  rot  due  to  Rhizoctonia. 


1916]  PARASITIC  RHIZOCTONIAS  IN  AMERICA  325 

EGGPLANT,  Solatium  melongena 

During  August,  1912,  while  some  field  observations  were  being 
made  on  carnation  stem  rot,  the  fruits  of  a  number  of  eggplants  in 
an  adjoining  field  were  found  to  be  rotting  at  the  point  where  they 
touched  the  ground.  The  decay  spread  in  all  directions  from  this 
point,  making  a  sunken,  brown  area ;  this  was  followed  by  the  soften- 
ing and  subsequent  collapse  of  the  surrounding  tissues.  Fruits  showing 
this  decay  were  brought  into  the  laboratory  and  placed  under  a  bell 
jar.  Around  the  diseased  spot  there  soon  developed  a  thick  mass  of 
mycelium,  which  on  microscopic  observation  was  found  to  consist  of 
hyphse  of  Fusarium  and  Rhizoctonia.  The  decaying  spots  contained 
no  fungous  threads,  but  were  completely  filled  with  bacteria.  On  plat- 
ing, pure  cultures  of  R.  Solani  were  obtained.  The  cause  of  the  pri- 
mary infection  is  not  known.  It  is  very  probable  that  both  the  Fusar- 
ium and  Rhizoctonia  entered  the  tissues  where  the  epidermis  had  been 
destroyed. 

In  July,  1913,  the  damping-off  of  a  number  of  eggplant  seedlings 
in  the  vegetable  greenhouses  was  noticed.  This  was  shown,  by  pure 
cultures  of  the  diseased  material,  to  be  due  entirely  to  Rhizoctonia. 
The  fungus  produced  the  characteristic  lesions  on  one  side  of  the  seed- 
lings at  the  surface  of  the  soil,  causing  the  stem  to  break. 

Atkinson,4  in  his  account  of  damping-off  diseases,  mentioned 
eggplant  seedlings  among  those  susceptible  to  attacks  of  the  sterile 
fungus  (Rhizoctonia).  Rolfs95  reported  the  presence  of  the  Corticium 
stage  of  Rhizoctonia  on  mature  plants  in  an  irrigated  garden.  Here 
the  plants  affected  drooped  for  a  time  and  then  wilted  and  died.  Le- 
sions were  formed  on  the  stems  at  the  surface  of  the  ground. 
Wolf140'141  in  1914  reported  damping-off  and  a  fruit  rot  of  eggplants 
due  to  Rhizoctonia  (Corticium  vagum  B.  &  C.),  but  he  does  not  re- 
gard the  fungus  as  the  cause  of  serious  injury  to  eggplants. 

FIVE-FINGER,  Potentilla  sp. 

A  number  of  five-finger  plants  were  found  to  be  infected  with 
R.  Solani  during  June,  1914,  in  inoculated  sections  in  the  floricul- 
tural  greenhouses.  The  mycelium  of  the  fungus  was  present  at  the 
nodes  which  touched  the  soil  and  also  at  the  bases  of  the  plants,  where 
crown  rot  was  developing. 

FOXTAIL  GRASS,  Setaria  glauca 

Several  plants  of  foxtail  grass  growing  under  the  same  conditions 
as  the  preceding  host,  five-finger,  showed  a  root  infection. 

GypsopMla  repens 

A  number  of  Gypsophila  repens  plants  were  found  diseased  in  the 
herbaceous  grounds  during  July,  1913.  Pure  cultures  of  the  diseased 


326  BULLETIN  No.  189  [June, 

material  showed  the  causal  organism  to  be  R.  Solani.  The  plants  were 
bushy,  so  that  some  of  the  branches  and  leaves  were  in  contact  with 
the  soil.  The  symptoms  and  appearance  of  the  disease  were  similar 
to  those  described  for  Dianthus. 

LAMB'S  QUARTERS,  Clienopodium  album 

During  the  summer  of  1913  several  wilted  Clienopodium  plants 
were  observed  along  the  border  of  the  old  herbaceous  grounds  of  the 
Station.  On  pulling  up  the  wilted  plants,  it  was  found  that  R.  Solani 
was  the  cause  of  the  wilting.  The  fungus  did  not  enter  very  deep 
into  the  tissues,  but  rather  girdled  the  stem  and  formed  a  scurfy  layer. 

Duggar  and  Stewart32  in.  1901  reported  the  occurrence  of  Rhizoc- 
tonia  on  Clienopodium  album. 

Lavatera  arborea  variegata 

During  March,  1913,  in  the  floricultural  greenhouses,  a  number  of 
seedlings  in  small  seed  pans,  among  which  were  several  pans  of  Lava- 
tera, began  to  damp  off  in  a  manner  characteristic  of  R.  Solani. 
Pure  cultures  of  diseased  seedlings  yielded  this  fungus.  Strands  of 
the  brown  mycelium  could  be  seen  on  the  surface  of  the  soil  and 
extending  up  on  the  stems  and  leaves.  This  was  noticed  again  in  the 
spring  of  1914. 

LETTUCE,  Lactuca  sativa 

Atkinson4  in  1895  mentioned  the  damping-off  of  seedling  lettuce, 
among  a  number  of  other  plants,  by  a  sterile  mycelium  which  later 
proved  to  be  Rhizoctonia. 

Stone  and  Smith128  found  that  R.  Solani  caused  a  rot  of  green- 
house lettuce,  altho  the  disease  was  not  common.  The  first  appearance 
was  on  the  lower  leaves  where  they  lay  on  the  ground ;  a  brown  rot 
set  in,  which  spread  thru  the  leaf  in  a  very  characteristic  manner. 
The  green  blade  rapidly  rotted  away,  leaving  the  midrib  and  stalk  as 
sound  as  tho  the  blade  had  been  carefully  cut  away  or  had  been  eaten 
by  insects. 

Duggar  and  Stewart32  observed  the  damping-off  of  lettuce  seed- 
lings by  Rhizoctonia  for  a  number  of  years.  They  found  that  at  or 
near  the  surface  of  the  ground  the  tissues  become  water-soaked  in 
appearance  and  unable  longer  to  support  the  seedling,  so  that  it  falls 
to  the  ground,  the  fungus  invading  all  parts.  Within  a  day  or  two 
this  fungus,  under  favorable  conditions,  wilted  do\vn  and  destroyed 
whole  boxes  of  lettuce  seedlings.  Duggar  and  Stewart  also  observed 
several  times  what  was  apparently  the  same  fungus  causing  a  disease 
of  mature  lettuce  plants.  On  the  older  leaves  the  leaf  blades  alone 
were  affected,  but  the  more  delicate  inner  leaves  succumbed  entirely, 
blackening  and  decaying  with  the  progress  of  the  disease. 


1916] 


PARASITIC  KHIZOCTONTAS  IN  AMERICA 


327 


Iii  1903  Selby104  reported  the  presence  of  a  rosette  disease  of  let- 
tuce, which  he  described  as  follows:  "The  plants  affected  showed, 
usually  not  long  after  transplanting,  but  occasionally  at  other  stages, 
a  failure  to  send  out  central  leaves  freely.  The  leaf-bearing  axis  re- 
mained shortened,  and  the  last  leaves  formed  remained  short,  making 
a  very  striking  contrast  to  the  remainder  of  the  plants  in  the  bed 
and  to  the  lower  leaves  of  the  same  plant.  (Frequently  the  plants 
overcome  this  tendency  and  make  a  fair  amount  of  product  with 
longer  time.)  Examination  of  the  roots  showed  areas  occupied  by 
the  hyphae  of  Rhizoctonia. "  In  1906  Selby106  treated  at  length  the 
control  of  rosette  in  lettuce  due  to  Rhizoctonia. 


Fio.   14. — DAMPINO-OFF  OF  LAVATERA  SEEDLINGS  BY  Bhizoctonia  Soldni 

(Experiment  9) 


328  BULLETIN  No.  189  [June, 

In  1905  Rolfs05  reported  the  presence  of  the  perfect  stage,  Cor- 
ticium  vagum  B.  &  C.,  on  lettuce  from  Florida. 

Lobelia  erinus  (Single  Blue) 

The  lobelia  plants  in  the  floricultural  greenhouses  in  1914  were 
small  and  sessile,  and  covered  the  tops  of  the  pots  in  which  they  were 
growing.  In  June  a  number  of  them  began  to  die.  On  close  exami- 
nation, strands  of  R.  Solani  could  be  seen  spreading  thru  the  mass  of 
plant  material.  The  low-lying  leaves  afforded  a  good  hiding  place 
for  sow  bugs,  and  no  doubt  they  helped  in  carrying  the  fungus  from 
one  pot  to  another.  Attacks  of  Rhizoctonia  on  other  varieties  of  lobelia 
have  been  observed  in  the  greenhouses  a  number  of  times. 

ONION,  Allium  sp. 

A  culture  of  Rhizoctonia  isolated  from  onion  seedlings  was  ob- 
tained from  Cornell  University  by  Mr.  H.  W.  Anderson  in  1911.  Since 
that  time  the  author  has  worked  with  this  strain  both  in  the  laboratory 
and  in  the  greenhouse.  From  its  morphological  and  physiological 
behavior,  it  must  be  classed  as  distinct  from  the  other  strains. 

Dr.  I.  C.  Jagger  states  in  a  letter  that  he  first  isolated  this  form 
from  onion  on  May  29,  1911,  from  seedlings  growing  on  muck  soil  in 
New  York.  He  found  that  the  Rhizoctonia  mycelium  was  always  con- 
fined to  the  first,  or  seed,  leaf  and  that  damping-off  ceased  as  soon  as 
the  second  leaves  had  developed. 

PANSY,  Viola  tricolor 

During  the  fall  of  1913  pansy  plants  were  placed  in  a  solid  bed, 
in  the  floricultural  greenhouse,  as  a  border  for  sweet  peas.  At  that 
time  some  of  the  sweet-pea  plants  died,  and  eventually  a  culture  of  R. 
Solani  was  obtained  from  them.  The  following  April  several  pansy 
plants  in  the  vicinity  of  the  spot  where  the  sweet  peas  had  died  became 
diseased  and  later  died.  A  culture  showed  the  trouble  to  be  due  to 
Rhizoctonia.  Later  a  large  number  of  the  plants  in  the  row  died.  The 
fungus  attacked  the  plant  at  the  crown  and  caused  a  rapid  rot.  The 
prostrate  branches,  the  petioles  of  the  leaves,  and  even  the  leaves  them- 
selves were  also  rotted  in  a  characteristic  fashion.  The  strands  of  the 
mycelium  could  easily  be  seen  ramifying  between  the  rotting  mass 
arid  the  soil. 

PLANTAIN,  Plantago  aristata 

Diseased  plants  of  plantain  were  found  during  June,  1914,  in 
inoculated  sections  in  one  of  the  floricultural  greenhouses.  The 
mycelium  of  R.  Solani  was  present  around  the  bulbous  base  of  the 


1916]  PARASITIC  EHIZOCTONIAS  IN  AMERICA  329 

plants,  causing  a  crown  rot.    In  one  or  two  cases  several  leaves  were 
completely  rotted  at  the  crown. 

POINSETTIA,  Euphorbia  pulcherrima 

About  October  7,  1912,  young  poinsettia  plants  were  taken  from 
the  cold  house  (50°  to  60 °C.)  of  the  flori cultural  greenhouses  and  put 
in  a  box  with  a  glass  top.  They  were  then  placed  near  the  cutting 
bench,  in  which  a  number  of  plants  of  various  kinds  were  damping  off. 
The  poinsettia  cuttings  shortly  afterwards  began  to  die  off  rapidly. 
The  characteristic  lesions  on  the  stems  of  the  young  plants  and  pure 
cultures  of  the  diseased  material  indicated  that  this  condition  was  due 
to  R.  Solani.  The  lesions,  instead  of  being  on  one  side  and  more 
or  less  localized,  in  almost  every  case  formed  a  collar  around  the  stem 
at  the  surface  of  the  soil.  The  collar  was  about  2  to  3  millimeters 
wide,  somewhat  depressed,  and  of  a  dark  color.  Strands  of  the  brown 
mycelium  were  visible  spreading  over  the  soil  in  the  pots.  This  infec- 
tion probably  had  its  origin  in  the  cutting  bench. 

POTATO,  Solanum  tuberosum 

On  the  potato  R.  Solani  exhibits  a  number  of  interesting  charac- 
teristics, which  vary  with  climatic  conditions,  age  of  the  host,  and  part 
of  the  plant  attacked. 

The  sclerotial  stage  of  this  fungus  has  been  observed  on  practically 
every  Illinois  potato  tuber  examined  by  the  writer.  Moreover,  in 
every  shipment  from  other  states  which  has  been  examined,  the  fun- 
gus has  been  found  present.  The  tubers  affected  were  dotted  with 
brownish  black  sclerotia  of  various  shapes  and  sizes  (Fig.  15),  but  so 
far  as  could  be  determined,  they  were  causing  no  direct  injury.  This 
type  of  Rhizoctonia  disease  of  potato  is  the  one  most  commonly  found 
in  the  United  States. 

R.  Solani  also  causes,  under  certain  conditions,  a  russeting,  or 
scab,  a  cracking  of  the  tuber,  the  formation  of  pits  at  or  near  the  len- 
ticels,  and  a  wet  rot  of  the  tuber.  These  types  of  injury  have  been  ob- 
served by  Rolfs92'93  in  Colorado,  by  Orton73  in  various  states,  and 
by  Morse  and  Shapovalov69  in  Maine. 

On  the  plant  itself  this  fungus  produces  various  types  of  diseases. 
In  many  cases  young  plants  are  completely  cut  off  before  they  reach 
the  surface  of  the  ground.  Older  plants  that  are  severely  attacked 
just  below  the  surface  of  the  ground  usually  die  off  quickly.  If  they 
are  only  slightly  attacked,  the  fungus  produces  small  lesions  on  the 
stems,  the  plants  take  on  a  dwarfed  and  unhealthy  appearance,  and 
the  tubers  remain  small,  altho  the  plants  usually  live  thru  the  sum- 
mer. When  the  stem  is  girdled  by  the  fungus  so  as  to  prevent  trans- 
location  entirely,  large  tops  are  produced,  aerial  tubers  are  formed, 


330 


BULLETIN  No.  1SU 


FIG.  15. — POTATO  TUBER  SHOWING  THE  SCLERGTIA.  OF  Rhizoctonia  Solani 


J.016]  PARASITIC  EUIZIHTONJAS  IN  AMKKICA  331 

and  in  some  cases  a  curling  of  the  leaves  or  resetting  results.  When 
the  main  stein  is  attacked  below  the  surface  of  the  soil  and  the  stolons 
are  cut  off,  the  condition  known  as  "little  potatoes"  is  produced;  in 
such  cases  a  cluster  of  small,  short-stemmed  tubers  is  formed  above 
the  wound.  The  production  of  aerial  potatoes,  rosette,  and  leaf  curl- 
ing also  occurs  when  the  stolons  are  attacked  and  the  young  tubers  arc 
cut  off. 

These  abnormal  developments  of  the  potato  are  usually  associated, 
and  are  secondary  physiological  effects  due  to  disturbances  of  the 
nutrition  of  the  plant.  They  occur  most  frequently  on  poorly  drained 
land  and  especially  on  heavy  soils. 

Rolfs92  attributed  the  potato  failure  of  1902-03  in  Colorado  to 
little  potato.  Selby103  in  Ohio,  in  his  studies  of  the  Rhizoctonia  dis- 
ease on  potato,  gave  particular  attention  to  rosette.  In  1914  Morse 
and  Shapovalov09  concluded  that  the  Rhizoctonia  disease  of  potato  is 
of  a  more  serious  nature  than  is  generally  considered.  In  one  field 
which  they  had  under  observation  for  several  seasons,  they  attributed 
the  poor  and  uneven  stands,  unexpected  low  yields,  early  ripening, 
and  death  of  the  tops  to  Rhizoctonia.  In  most  cases  they  confirmed 
the  observations  made  by  Rolfs.  Recently  investigators  all  over  the 
country  have  been  emphasizing  the  serious  nature  of  the  disease. 

In  January,  1915,  material  of  Rhizoctonia  Crocorum  on  potato 
tubers  was  received  from  Mr.  F.  D.  Bailey  of  the  Oregon  Agricultural 
Experiment  Station.  On  comparing  it  with  Rhizoctonia  Solani,  it  was 
found  to  be  entirely  different  in  all  respects.  However,  this  fungus  is 
identical  with  the  fungus  on  alfalfa  reported  by  a  number  of  observers 
(Webber,  Heald,  and  Freeman)  as  R.  Crocorum.  Thus  it  appears 
that  R.  Crocorum  is  present  in  this  country  on  alfalfa  and  on  potato 
tubers. 

Bailey8  describes  the  Rhizoctonia  disease  of  potato  as  follows : 

' '  The  surface  was  almost  entirely  covered  with  a  dense,  felt-like  mat  of  a 
chocolate  color  when  dry,  violet -brown  when  moist.  This  mat  was  found  to  be 
composed  of  mycelium  which  had  long  narrow  cells  and  a  branching  habit  char- 
acteristic of  Rhizoctonia.  The  greater  part  of  this  mycelial  mat  could  be  easily 
removed,  and  beneath  this  the  surface  of  the  tuber  was  covered  with  very  small 
dark  spots.  These  spots  appeared  to  the  unaided  eye  as  minute  eruptions  of  the 
skin.  Under  the  microscope  one  can  see  the  mycelial  threads  attached  at  these 
points,  and  a  freehand  section  thru  such  a  spot  shows  it  to  be  a  structure  com- 
posed entirely  of  interwoven  fungus  threads  forming  a  sclerotium.  No  evidence  of 
differentiation  or  any  type  of  spore  formation  within  this  body  could  be  found 
on  examination  of  many  sections.  The  portion  of  the  sclerotium  near  the  sur- 
face is  composed  of  cells  that  are  very  deeply  colored,  giving  the  black  appear- 
ance. The  outer  surface  of  the  sclerotium  is  seen  to  project  above  the  surface, 
while  the  lower  or  underlying  portion  is  embedded  in  the  outer  cortical  layers 
of  cells  of  the  tuber.  Furthermore,  there  is  a  strand  of  fungus  tissue  extending 
deeper  than  the  sclerotium,  which  connects  it  with  a  layer  of  the  same  type  of 
fungus  tissue  spreading  between  the  cortex  and  parenchyma  from  the  poini  where 
this  strand  reaches  the  parenchyma. 

"Attempts  to  grow  this  fungus  in  culture  failed.  This  has  been  the  experience 
reported  in  attempts  to  grow  Khisoctonia  violacea  Tul. " 


332 


BULLETIN  No.  189 


RADISH,  Eaphanus  sativus 


[June, 


Damping-off  of  radish  seedlings  by  R.  Solani  has  appeared  sev- 
eral times  in  the  floricultural  greenhouses.  During  May,  1914,  an  at- 
tack of  Rhizoctonia  on  mature  radishes  was  observed  in  the  writer's 
home  garden.  The  first  sign  of  the  disease  was  the  yellowing  of  the 
foliage,  followed  by  the  wilting  of  the  leaves.  On  pulling  up  a 
plant,  the  crown  was  found  to  be  rotted  at  the  base  of  the  leaves.  The 
rot  progressed  slowly  and  killed  only  a  few  of  the  plants.  After  it 
had  proceeded  for  some  length,  the  radishes  cracked  farther  down. 
This  is  very  characteristic  of  the  disease  at  this  stage  (Fig.  16). 

In  1895  the  damping-off  of  radish  seedlings  by  a  sterile  fungus, 
which  was  later  identified  as  Rhizoctonia,  was  first  reported  by  Atkin- 
son.4 Duggar  and  Stewart32  in  1901  noted  a  disease  caused  by  Rhi- 
zoctonia of  mature  radishes  forced  in  a  greenhouse.  The  disease 
caused  a  soft  rot  of  the  crown  or  lesions  in  this  region.  The  leaves 
were  generally  unaffected  until  a  large  part  of  the  root  had  decayed. 
Plants  in  all  stages  of  growth  were  affected  and  killed.  Duggar  and 
Stewart  also  found  a  Rhizoctonia  in  connection  with  the  damping-off 
of  radish  seedlings  in  the  greenhouse. 


FIG.  16. — LATE  STAGE  OF  ROOT  EOT  OF  RADISHES  CAUSED  BY  Rhizoctonia  Solani 


1916]  PARASITIC  RHIZOOTOXTAS  IN  AMERICA  333 

In  1904  Clinton14  observed  a  damping-off  and  root  rot  of  radish 
due  to  Rhizoctonia.  Apparently  the  disease  was  not  very  serious. 
Stewart125  in  1910  also  reported  a  damping-off  and  root  rot  of  radish 
due  to  Ehizoctonia.  Infection  took  place  first  at  the  level  of  the  soil, 
causing  the  leaves  to  have  a  wilted,  drooping  appearance.  From  this 
point  the  disease  spread  into  the  leaves  and  roots  of  the  plant,  soon 
causing  death.  On  mature  radishes,  decayed  spots  of  irregular  shape 
were  produced,  and  at  an  advanced  stage  the  diseased  portions  of  the 
plant  were  covered  with  a  white,  felted  mycelium. 

RHUBARB,  Rheum  rhaponticum 

In  1901  Duggar  and  Stewart32  reported  a  disease  of  rhubarb,  on 
Long  Island,  which  they  had  had  under  observation  for  several  years. 
They  described  the  disease  as  follows : 

' '  An  unthrifty  condition  of  the  plants  was  noticed,  followed  by  the  rapid 
dying  off  of  many  of  the  leaves.  The  affected  leaves  became  dry  and  shrunken 
in  appearance  and  soon  fell  to  the  ground.  Where  a  field  was  badly  affected, 
the  majority  of  hills  showed  the  trouble  to  the  extent  of  at  least  a  leaf  or  two. 
In  several  instances  from  one-fourth  to  three-fourths  of  the  leaves  were  already 
dead.  An  affected  leaf  breaks  off  readily  just  beneath  the  surface  of  the  ground, 
and  old  dead  leaves  rotted  off  in  this  region.  The  general  appearance  reminded 
one  strongly  of  the  effect  of  Rhizoctonia  upon  beets.  There  was  very  little  super- 
ficial mycelium  visible  to  the  unaided  eye.  Microscopic  examination  showed 
hyphse  of  a  Rhizoctonia  both  superficially  and  immediately  under  the  surface  where 
the  leaves  were  rotting." 

Clinton14  has  also  reported  a  stem  rot  of  rhubarb  due  to  Rhizoc- 
tonia. He  found  the  fungus  at  the  base  of  leaf  petioles,  causing  dark, 
sunken  cankers. 

SALVIA,  Salvia  splendens 

The  symptoms  of  the  Rhizoctonia  disease  of  salvia  observed  in  the 
flori cultural  greenhouses  were  similar  to  those  described  for  coleus. 
All  varieties  of  the  cuttings  in  the  bench  seemed  to  be  equally  suscep- 
tible. It  has  been  shown  that  the  serious  damping-off  of  the  salvia,  al- 
ternanthera,  and  coleus  was  due  to  the  fungus  which  was  first  brought 
in  on  the  mature  alternanthera  plants  from  which  cuttings  were  made. 
(See  Alternanthera,  page  310.) 

Santolina  chamcecyparissus 

In  1914  a  number  of  plants  of  Santolina  chamcecyparissus  growing 
in  pots  next  to  the  Centaurea  gymnocarpa  in  the  floricultural  green- 
houses, were  found  to  have  a  typical  stem  rot,  due  to  R.  Solani,  very 
similar  to  the  disease  as  described  for  that  plant  (see  page  321).  The 
fungus  could  be  distinctly  seen  running  thru  the  bushy  branches. 


334  BULLETIN  No.  189  [June, 

Sedum  sp. 

A  few  plants  of  Sedum  anglicum,  together  with  several  other  spe- 
cies of  Sedum,  were  found  diseased,  in  July,  1913,  in  the  herbaceous 
grounds.  The  progress  of  the  disease  was  very  slow ;  few  plants  were 
killed  during  the  entire  summer.  For  the  most  part,  the  fungus 
seemed  to  live  saprophytically  at  the  base  of  the  plant.  It  was  also 
found  on  healthy  plants  of  this  genus..  About  six  species  were  planted 
in  a  row  in  the  garden,  and  all  were  affected  in  much  the  same  way. 

SORREL,  Rumex  acetosella 

In  June,  1914,  a  number  of  sorrel  plants  were  found  diseased  in 
an  inoculated  section  in  the  greenhouse.  The  stems  of  the  plants  were 
covered  with  the  brown  strands  of  mycelium,  and  a  few  of  the  leaves 
were  rotted  off  at  the  crown.  Pure  cultures  of  the  diseased  parts 
yielded  R.  Solani  in  every  case. 


During  July,  1912,  when  the  young  sweet  peas  in  the  field  were 
about  one-third  to  one-half  grown,  occasional  vines  showed  evidence 
of  disease  by  turning  yellowish,  wilting,  and  finally  drying  up  en- 
tirely. An  examination  of  the  affected  plants  showed  that  they  were 
more  or  less  separated  from  their  roots  near  the  surface  of  the  ground. 
Pure  cultures  of  the  diseased  material  yielded  R.  Solani  in  all  cases. 

In  November,  1913,  several  diseased  seedlings  were  brought  in  from 
the  plant-breeding  greenhouses.  On  close  examination  the  stems 
showed  the  characteristic  lesions  caused  by  Rhizoctonia.  The  same 
trouble  occurred  in  the  floricultural  greenhouses  the  past  two  seasons, 
but  in  no  case  was  it  severe. 

During  the  winter  of  1913,  the  writer  was  called  to  Chicago  to  look 
over  a  range  of  greenhouses  devoted  to  the  growing  of  sweet  peas. 
Sweet-pea  plants  of  all  ages  were  seriously  affected.  Dead  plants  were 
scattered  thru  the  whole  house.  Close  examination  of  the  diseased 
plants  revealed  the  fact  that  Rhizoctonia  was  causing  the  trouble. 
Apparently  it  started  in  the  seed  pans  and  continued  to  work  until  the 
plants  were  ready  to  be  discarded.  The  symptoms  in  each  case  were 
the  same — yellowing  of  the  foliage,  followed  by  the  wilting  and  dry- 
ing up  of  the  plants.  Characteristic  lesions,  which  finally  cut  the 
stems  off  at  the  surface  of  the  soil,  could  always  be  found  on  the  dis- 
eased plants.  The  root  systems  were  much  dwarfed. 

In  1908  Clinton16  observed  in  Connecticut  a  damping-off  of  sweet 
peas  due  to  Rhizoctonia.  Taubenhaus130'131  in  describing  a  Rhizoc- 
tonia rot  of  sweet  pea  at  different  stages,  states  that  he  found  it  quite 
destructive  to  the  plants  when  they  are  in  the  seedling  stage. 


I'AHA.SITIC  RimCKTOXlAS  IX  AMERICA  335 

TOBACCO,  Nicotiana  sp. 

In  1904  Clinton14  noticed  a  seed-bed  rot  of  tobacco,  which  he 
thought  was  due  to  Rhizoctonia.  The  same  year  Selby105  observed  a 
similar  bed  rot  of  tobacco  in  Ohio  caused  by  Rhizoctonia.  He  stated 
that  the  specific  characteristics  of  the  fungus  do  not  differ  essentially 
from  those  of  its  forms  on  other  plants,  including  potato. 

Clinton,15  in  making  another  report  on  this  disease,  in  1906,  stated 
that  the  injury  to  the  plants  was  slight  and  was  confined,  as  with  the 
potato,  to  the  underground  parts. 

Johnson63  has  carried  on  some  extensive  work  on  Rhizoctonia,  with 
a  view  to  controlling  the  damping-off  of  tobacco  seedling^. 

TOMATO,  Lycopersicum  esculentum 

A  damping-off  disease  of  tomatoes  caused  by  Rhizoctonia  has  been 
noted  from  a  number  of  states;  the  symptoms  of  the  disease  are  the 
same  as  have  been  described  for  a  number  of  other  plants,  such  as 
eggplant. 

In  connection  with  his  wrork  011  the  potato  rosette  resulting  from 
Rhizoctonia,  Selby104  also  mentioned  a  tomato  rosette  caused  by  the 
same  fungus.  He  stated  that  the  tips  of  diseased  plants  showed 
rather  long  internodes  and  dwarfed  leaves,  with  somewhat  curled-leaf 
aspects,  while  the  roots  had  lesions  and  other  similar  features  found 
in  potato  rosette. 

.  Rolfs95  in  1905  stated  that  he  frequently  found  the  Corticium  stage 
on  the  tomato  plant,  but  that  apparently  the  plants  do  not  suffer  ma- 
terially from  its  presence  when  planted  on  well-aerated  land.  He 
described  it  as  follows : 

"The  fruiting  stage  of  the  fungus  develops  freely  on  the  stem  just  above  the 
surface  of  the  ground,  often  extending  up  the  stem  for  a  distance  of  six  inches. 
As  a  rule  the  fungus  does  not  penetrate  the  tissue  here,  but  simply  covers  the  stem 
of  the  plant.  The  tomatoes  which  touch  the  ground  are  frequently  more  or  less 
covered  by  a  fruiting  membrane  of  the  fungus,  which  mars  the  appearance  of  the 
ripe  fruit.  So  long  as  the  tomatoes  are  green  and  the  skin  uninjured,  the  fruit 
remains  sound ;  however,  if  the  skin  is  ruptured,  the  fungus  soon  destroys  it,  pro- 
ducing a  brown  rot.  This  organism  also  frequently  gains  entrance  to  the  fruit  at 
the  stem  end." 

Orton72  described  the  rosette  of  tomato  caused  by  Corticium  vagum 
B.  &  C.  as  a  disease  of  minor  importance  in  tomato  culture.  He  stated 
that ' '  the  fungus  attacks  the  roots  and  base  of  the  stem,  forming  dark 
cankers.  The  effect  on  the  plant  is  to  dwarf  and  curl  the  leaves  and 
to  restrict  productiveness." 

A  fruit  rot  of  the  tomato  has  also  been  observed  by  Pool86  and 
again  by  Wolf.141  Pool  described  the  symptoms  of  the  fruit  rot  as 
follows : 

' '  The  specimen  examined  showed  no  rupture  in  the  external  skin  visible  to 
the  naked  eye.  The  diseased  area  was  plainly  distinguishable  by  the  chocolate- 


336  BULLETIN  No.  189  [June, 

colored,  slightly  wrinkled  epidermis.  An  examination  of  the  underlying  tissues 
revealed  the  same  general  color  and  numerous,  somewhat  darkened  filaments  pene- 
trating the  cells  in  all  directions." 

Wollenweber1 42  in  1913  described  a  species,  Rhizoctonia  poto- 
macensis  Wr.,  which  causes  a  fruit  rot  of  green  tomatoes.  He  stated 
that  this  species  differs  from  Rhizoctonia  Solani  in  the  character  of 
its  attacks,  in  that  concentric,  subepidermal  mycelial  zones  are  formed 
within  the  tomatoes. 

VIOLET,  Viola  odorata 

During  ^he  fall  of  1913  a  number  of  violet  plants  in  the  floricul- 
tural  greenhouses  were  found  to  be  diseased.  A  few  had  stem  rot, 
while  on  others  only  the  bases  of  the  petioles  were  somewhat  rotted. 
Where  the  pots  were  set  close  together  and  the  plants  overlapped,  the 
brown  strands  of  R.  Solani  could  be  plainly  seen  spreading  out  from 
one  plant  to  another.  However,  in  no  case  was  the  disease  severe ;  it 
is  probable  that  the  fungus  was  living  saprophytically  on  the  lower 
leaves. 

Duggar  and  Stewart32  observed,  in  a  greenhouse  in  New  York,  one 
case  of  destructive  violet  stem  rot  due  to  Rhizoctonia  and  a  second 
case  similar  to  the  attack  described  above. 

ADDITIONAL  OBSERVATIONS 

Beside  the  hosts  that  have  been  mentioned,  observations  have  been 
made  in  the  floricultural  greenhouses  of  diseased  seedlings  and  cut- 
tings of  a  number  of  other  plants,  tho  no  work  has  been  done  further 
than  to  make  a  microscopic  examination  of  the  diseased  material. 

Below  is  a  list  of  seedlings  and  cuttings  found  damping  off  in  the 
spring  and  fall  of  1914,  with  the  percentage  of  loss  resulting.  In  all 
cases  Rhizoctonia  proved  to  be  the  cause  of  the  trouble. 

Percentage 

Seedlings  Damping  off,  April  6,  1914  of  loss 

Amaranthus  caudatus   75 

salicifolius    90 

Bartonia  aurea   90 

Calendula  Pongei  1-2 

Celosia  Huttoni,  var.  Thompsonii  magnifica 75 

Chrysanthemum  hortorum    30-40 

Dianthus  chinensis  80 

Heddewigii     30 

latifolius     80 

Godetia  sp 80 

Gypsophila  muralis   30 

Kochia  trichophylla  99 

Lavatera  arborea  variegata 5 

Linaria  Maroccana  5 

Linum  grandiflorum  rubrum 30 

Lychnis  coeli  rosa 90 

Portulaca  oleracea   80 

Schisanthus  sp 2-4 


1916]  PARASITIC  EHIZOCTONIAS  IN  AMERICA  337 

Percentage 

Seedlings  Damping  off,  September  2,  1914  of  loss 

Aqullegia  (6  species)  85 

Campanula  (8  species)    80 

Cineraria  (several  species)    20 

Dianthus  plumarius   85 

Erysimum  pulchellum   2 

Linaria  Cyinbalaria 2 

Lythrum  sp 2 

Matthiola  incana  (stocks)    2 

Primula  malacoides  2 

' '        obconica  grandiflora    2 

Schizanthus  (mixed)    2 

Kilene  Schafta    100 

Stachys  lanata  2 

Viola  tricolor  (3  varieties)    20 

Cuttings  Damping  off,  September  25,  1914 

Abutilon  hybridv/m,  var.  Savitzii 100 

Acalypha  Wilkesiana,  var.  bicolor 100 

tricolor     100 

"                                 "     marginata    90 

Ageratum  mexicanum  vars 2 

Alyssum  odoratum  (3  varieties)    100 

Coleus  (10  varieties)    2 

Cuphea  platycentra   2 

Iresine  (Achyranthes)  (5  varieties)  95 

Petunia  (several  varieties)   100 

Piqueria  trinervia  (Stevia) 100 

Santolina  chamcecyparissus 2 

Sedum  spectabile 2 

Telanthera  (Alternanthera)  (9  varieties) 2 

Vinca  major  (several  varieties)  2 

TYPES  OF  SYMPTOMS 

From  a  study  of  the  symptoms  caused  by  Rhizoctonia  Solani  on 
the  various  hosts,  it  is  seen  that,  except  for  a  few  minor  points,  they 
are  the  same  when  appearing  on  the  same  type  of  host.  The  damping- 
off  of  seedlings  and  cuttings  of  various  plants  is  identical,  as  is  the 
rotting  of  a  number  of  root  crops.  In  most  herbaceous  plants  a  stem 
rot  is  produced,  the  symptoms  of  which  are  also  identical  on  the  vari- 
ous hosts.  On  very  resistant  plants  lesions  only  are  formed ;  these  are 
apparently  identical  on  the  different  hosts. 

INOCULATION  EXPERIMENTS 

The  main  purpose  of  these  inoculation  experiments  was  to  ascer- 
tain the  degree  of  biologic  specialization  which  may  exist  between  the 
various  cultural  strains  of  Rhizoctonia,  or  between  strains  isolated 
from  different  hosts  or  of  different  geographical  origin.  With  three 
thousand  square  feet  of  glass  available  in  the  floricultural  greenhouses 
and  with  the  assistance  of  the  members  of  the  floricultural  division,  it 
was  possible  to  carry  on  cross-inoculation  experiments  involving  about 


338  BULLETIN  No.  189  [June, 

3,000  cuttings,  2,000  plants,  and  7,000  seedlings  of  various  kinds.  With 
these,  comparisons  were  made  of  about  forty-five  strains  of  Rhizoctonia. 
A  large  number  of  the  strains  used  in  these  experiments  were  iso- 
lated by  the  writer  from  the  various  hosts  found  infected  with  Rhizoc- 
tonia in  this  vicinity.  Other  strains  were  obtained  from  various  in- 
vestigators thruout  the  country.  Below  is  presented  a  list  of  the  strains 
used  and  the  source  of  each. 

Alfalfa. — A  Rhizoctonia  culture  from  alfalfa  was  received  from  Dr.  C.  W. 
Edgerton,  Baton  Rouge,  Louisiana,  November  12,  1912.  It  was  originally  ob- 
tained by  Dr.  Edgerton  in  May,  1910,  from  alfalfa  seedlings. 

Alternanthera  B.A.C. — -A.  culture  of  Rhizoctonia  was  isolated  from  infected 
alternanthera  cuttings  found  in  the  floricultural  greenhouses  in  the  fall  of  1912. 

Alternanthera  R.A.F. — This  strain  was  obtained  at  the  same  time  as  the 
preceding,  from  mature  alternanthera  plants  in  the  field. 

Amaranthus. — In  August,  1913,  Mr.  W.  H.  Burkholder,  of  Cornell  University, 
contributed  several  specimens  of  AinarantTws  retroflexus  infected  with  Rhizoc- 
tonia, from  Irving,  New  York.  The  stems  were  covered  with  the  immature,  gray, 
felt-like  mycelium  of  the  Corticium  stage.  Scrapings  of  the  hymenial  layer  of 
this  stage  yielded  pure  cultures  of  Rhizoctonia  in  every  case. 

Aster. — Early  in  1913,  Dr.  F.  A.  Wolf  sent  to  the  writer  a  culture  of  Rhizoc- 
tonia which  was  the  cause  of  the  damping-off  of  China  aster  seedlings  in  flats 
in  the  greenhouse  at  Auburn,  Alabama. 

Bean. — A  transfer  of  a  culture  of  Rhizoctonia  from  bean  was  obtained  in 
December,  1912,  from  Dr.  J.  T.  Barrett,  of  this  university.  He  in  turn  had  re- 
ceived it  from  Dr.  M.  F.  Barrus,  of  Cornell  University,  about  1910. 

Beet. — A  culture  of  Rhizoctonia  was  obtained  from  young  seedlings  of  the 
garden  beet  found  damping  off  in  the  vegetable-gardening  greenhouses,  July  10. 
1913. 

Begonia. — The  strain  from  begonia  was  isolated  by  Mr.  Anderson  from  cut- 
tings found  damping  off  in  the  floricultural  greenhouses  in  the  fall  of  1911. 

Carnation. — During  the  season  of  1911-12,  Mr.  Anderson  isolated  Rhizoctonia 
from  a  number  of  carnation  plants  received  from  different  sources,  and  during 
1912-13  and  1913-14  the  work  was  continued  by  the  author,  so  that  a  comparison 
of  a  large  number  of  cultures  from  diseased  plants  obtained  from  various  localities 
was  possible.  The  strains  used  are  given  below. 

"Carnation  R.K. ":  Isolated  by  Mr.  Anderson  from  diseased  carnation 
plants  obtained  at  Urbana,  Illinois,  in  October,  1911. 

"Carnation  R.O. ":  Culture  isolated  by  Mr.  Anderson  in  the  fall  of  1911, 
at  Urbana. 

"Carnation  R.H. ":  Culture  isolated  from  a  diseased  plant  in  the  floricul- 
tural greenhouses  in  the  fall  of  1911  by  Mr.  Anderson. 

"Carnation  R.S. ":  Isolated  from  diseased  plants  received  from  Kankakee, 
Illinois,  by  Mr.  Anderson,  October  25,  1911. 

"Carnation  R.  2":  Culture  reisolated  by  Mr.  Anderson  from  infected  cut- 
tings in  sterilized  soil  in  the  spring  of  1912. 

"Carnation  R.F. ":  Isolated  from  diseased  carnation  plants  gathered  in  the 
field  in  the  horticultural  grounds,  July  24,  1912. 

"Carnation  R.M.2":  Isolated  from  a  White  Enchantress  plant  in  one  of 
the  floricultural  greenhouses  during  September,  1912. 

' '  Carnation  R.  107 ' ' :  Obtained  from  a  plant  in  the  floricultural  greenhouses, 
September  7,  1912. 

"Carnation  R.F.2":  Culture  obtained  from  a  diseased  plant  in  the  field 
during  the  summer  of  1913. 

"Carnation  R.  121-5":  A  reisolation  of  Rhizoctonia  was  obtained  on  De- 
cember 3,  1912,  from  a  diseased  plant  in  one  of  the  inoculated  sections  of  tho 
greenhouse. 

Carrot. — The  strain  of  Rhizoctonia  from  carrot  used  in  this  work  was  ob- 
tained by  Mr.  Anderson  from  Cornell  University  in  1911.  Nothing  is  known  of 
the  origin  of  the  culture. 


1916]  PARASITIC  RHIZOCTONIAS  ix  AMERICA  339 

Cauliflower. — A  culture  of  Rhizoetonia  from  cauliflower  was  obtained  in  1912, 
from  Dr.  C.  W.  Edgerton,  Baton  Bouge,  Louisiana.  This  culture  was  isolated 
from  diseased  cauliflower  seedlings  in  the  summer  of  1912,  so  that  it  was  a 
comparatively  fresh  culture  when  received  here. 

Clienopodium. — A  culture  was  isolated  during  the  summer  of  1913  from  ma- 
ture plants  of  Chenopodium  album  growing  along  the  border  of  the  old  herbaceous 
grounds  back  of  the  floricultur,al  greenhouses. 

Clover. — A  culture  of  Rhizoctonia  from  red-clover  roots  was  received  from 
Mr.  E.  A.  Arzberger,  Wooster,  Ohio,  March  3,  1913.  The  fungus  was  isolated 
by  him  from  red-clover  roots  in  the  greenhouse  in  December,  1912. 

Coleus  I. — This  strain  was  obtained  from  coleus  cuttings  found  damping  off 
in  the  floricultural  greenhouses,  November,  1912. 

Coleus  II. — A  culture  was  isolated  from  coleus  seedlings  damping  off  in  seed 
pans,  October,  1913,  in  the  floricultural  greenhouses. 

Corn. — The  strain  from  corn  was  obtained  from  Dr.  J.  J.  Taubenhaus,  New- 
ark, Delaware,  in  1912.  He  stated  that  the  fungus  had  been  isolated  from  corn 
seedlings  that  were  damping  off  in  the  greenhouse. 

Cotton. — Three  cultures  of  Rhizoctonia  from  cotton  received  from  two 
sources  at  different  times,  were  used  in  these  experiments.  The  strain  ' '  Cotton  I ' ' 
was  received  from  Dr.  C.  W.  Edgerton,  Baton  Rouge,  Louisiana,  November  12, 
1912.  This  strain  was  cultured  by  him  in  September,  1911,  from  young  diseased 
plants.  The  strain  ' '  Cotton  II ' '  was  also  received  from  Dr.  Edgerton.  This 
strain  was  cultured  in  February,  1912,  from  the  same  kind  of  material  as  the 
above.  The  third  strain,  "Cotton  III,"  was  received  from  Dr.  F.  C.  Wolf, 
Auburn,  Alabama,  December  12,  1912.  The  fungus  was  isolated  from  seedling 
cotton  plants  growing  in  the  station  greenhouse  at  Auburn. 

Dlanthus. — Cultures  of  Rhizoctonia  were  isolated  during  July,  1913,  from 
diseased  plants  of  several  species  of  Dianthus  growing  in  the  perennial  garden. 
The  strains  cultured  and  used  in  the  experiments  were  ' '  D.  b'arbatus  N.  P., "  "  D. 
barbatus  S.  M., "  "  D.  plumarius, ' '  and  ' '  D.  sequeri. ' ' 

Eggplant. — Two  strains  of  Rhizoctonia  were  isolated  from  eggplant:  one, 
causing  a  fruit  rot,  was  cultured  August,  1912 ;  the  other  was  isolated  from  seed- 
lings damping  off  in  flats  in  the  vegetable-gardening  greenhouse,  July,  1913. 

Gypsophila  repens. — A  culture  of  Rhizoctonia  was  isolated  during  July,  1913, 
from  diseased  Gypsophila  plants  in  the  perennial  garden. 

Lavatera. — A  culture  was  isolated  in  1913  from  seedlings  of  lavatera  found 
damping  off  in  pans  in  the  floricultural  greenhouses. 

Lettuce. — The  strain  from  lettuce  was  obtained  by  Mr.  Anderson  in  1911, 
from  Cornell  University. 

Poinsettia. — Cultures  were  obtained  from  damping-off  poinsettia  cuttings 
found  in  the  floricultural  greenhouses,  October,  1912. 

Potato. — Several  strains  from  potato  were  used  in  these  experiments.  Two 
of  these  strains  were  obtained  from  scrapings  o-f  the  hymenial  layer  of  the  Corti- 
cium  stage. 

"Potato  R.P.C. " — A  culture  of  this  strain  was  isolated  from  fresh  potato 
stems  received  from  Dr.  I.  C.  Jagger,  Williamson,  New  York,  September  2,  1912. 
This  material  contained  the  perfect  stage,  Corticium  vagum  B.  &  C.  Pure  cul- 
tures of  Rhizoctonia  were  obtained  from  scrapings  of  the  hymenial  layer. 

"Potato  R.P.I." — In  response  to  a  letter  from  Mr.  Anderson,  Dr.  Geo.  H. 
Pethybridge,  Clifden  county,  Galway,  Ireland,  sent  a  small  box  of  potato  stems 
containing  the  perfect  stage,  Corticium  vagum  B.  &  C.  This  material  was  sent  by 
post,  July  18,  1912,  and  received  August  5.  A  pure  culture  of  Rhizoctonia  was 
obtained  from  scrapings  of  the  gray  mycelium  of  the  Corticium  stage. 

' '  Potato  R.P.O. ' ' — A  culture  from  potato  was  obtained  by  Mr.  Anderson 
from  Cornell  University.  The  strain  was  old  and  grew  very  poorly  on  agar. 

"Potato  R.  Sol." — This  strain,  like  the  preceding  one,  was  obtained  by  Mr. 
Anderson  from  Cornell  University.  It  also  grew  very  poorly  on  agar. 

Eadish. — A  culture  of  Rhizoctonia  from  radish  was  obtained  from  Cornell 
University,  by  Mr.  Anderson,  in  1911.  This  form  was  very  old  and  probably  had 
been  in  culture  several  years.  It  was  lost  in  April,  1913. 


340 


BULLETIN  No.  189 


[June, 


Salvia. — The  strain  from  salvia  was  isolated  from  cuttings  which  were  found 
in  the  same  bench  with  a  number  of  other  cuttings  damping  off,  October,  1912. 

Sedum. — A  culture  of  Ehizoctonia  from  sedum  was  isolated  from  diseased 
plants  found  in  the  herbaceous  grounds  in  July,  1913. 

Sugar  Cane. — A  culture  of  Ehizoctonia  isolated  from  sugar  cane  was  re- 
ceived from  Dr.  C.  W.  Edgerton,  November  12,  1912.  This  culture  was  obtained 
in  April,  1912.  It  was  fresh  and  virulent. 

Thistle. — A  culture  of  Ehizoctonia  from  thistle  was  obtained  by  Mr.  Ander- 
son from  Cornell  University  in  1911. 


The  method  of  infecting  the  cuttings,  seedlings,  and  young  plants 
grown  in  flats  and  benches,  was  as  follows :  Small  flats,  varying  in  size 
with  the  experiment,  were  first  soaked  in  a  strong  solution  of  formalin 
for  several  minutes  and  then  allowed  to  dry.  Steam-sterilized  sand 

or  soil  and  a  soil  culture  of  Rhi- 
zoctonia  were  then  mixed  to- 
gether in  the  flats  and  watered. 
After  being  tamped  down,  the 
flats  were  left  standing  for  two 
days  in  order  to  allow  the  fun- 
gus to  spread  thru  the  soil. 
Later,  the  cuttings,  seeds,  or 
plants  were  put  in  the  flats  and 
placed  in  a,  chamber  in  the  green- 
house where  the  moisture  could 
be  controlled.  Bottom  heat  was 
furnished.  The  temperature  var- 
ied somewhat  during  the  experi- 
ment, but  the  average  was  about 
60°  F.  When  only  individual 
plants  in  pots  or  in  benches  were 
to  be  infected,  a  portion  of  a  cul- 
ture of  Rhizoctonia  two  weeks 
old  on  green-bean  plugs  was 
placed  in  contact  with  the  stem 
of  each  plant  about  one-half 
inch  below  the  surface  of  the  soil, 
where  it  would  be  protected  from 
light  and  desiccation. 

In  obtaining  soil  cultures  of 
Rhizoctonia  in  large  quantities. 
Mason  jars  with  modified  covers 
were  found  to  be  very  suitable 
containers.  A  hole  about  one 
inch  in  diameter  was  cut  in  the 


FIG. 


17. — SOIL  CULTURE 
KHIZOCTONIA 


OF 


1916]  PARASITIC  BHIZOCTONIAS  IN  AMERICA  341 

center  of  the  cover,  and  a  small  tin  tube  about  two  inches  long  was  in- 
serted and  soldered  in.  This  hole  was  plugged  with  cotton.  (See 
Fig.  17.)  A  mixture  of  200  grams  of  dry  sand  and  10  grams  of  corn 
meal  was  then  placed  in  the  jars  and  moistened  with  distilled  water 
until  the  sand  was  wet  thru.  The  jars  and  their  contents  were  then 
sterilized  for  one  hour  at  twenty  pounds  pressure  in  an  autoclave,  after 
which  the  sand  was  inoculated  with  a  small  piece  of  infected  green- 
bean  plug  upon  which  Khizoctonia  was  growing  luxuriantly.  In  about 
a  month  the  soil  was  permeated  with  the  mycelium,  and  numerous 
brown  sclerotia  of  various  sizes  were  formed.  When  smaller  amounts 
of  infected  soil  were  needed,  a  250-cc.  flask  was  used. 

No  plant  was  listed  as  diseased  until  a  pure  culture  of  Rhizoctonia 
had  been  isolated  from  it.  Pure  cultures  were  easily  obtained  by  soak- 
ing small  pieces  of  diseased  parts  in  1-1000  mercuric  chlorid  for  two 
minutes  and  then  placing  them  on  green-bean  agar.  Rhizoctonia 
developed  rapidly,  and  in  twenty-four  to  forty-eight  hours  would 
spread  out  from  the  diseased  parts. 

EXPERIMENTS  1  AND  IA:  INOCULATION  OF  CARNATION  CUTTINGS  WITH 
VARIOUS  STRAINS  OF  RHIZOCTONIA 

Rhizoctonia  is  the  fungus  most  commonly  found  causing  a  damp- 
ing-off  of  carnation  cuttings  in  the  greenhouse.  To  determine  whether 
any  of  the  strains  from  sources  other  than  carnation  are  able  to  attack 
carnation  cuttings  with  the  same  ease  as  those  from  carnation,  the  fol- 
lowing experiment  was  carried  out.  Nine  hundred  carnation  cuttings 
and  28  strains  were  used  in  1913,  and  1,725  cuttings  and  34  strains 
in  1914. 

Sterilized  flats  (7x10  inches)  were  filled  with  sterilized  sand;  a 
250-cc.  soil  culture  of  Rhizoctonia  was  then  added  to  each  and  the 
sand  tamped  down  and  watered.  One  flat  was  left  uninoculated  to 
serve  as  a  check.  After  two  days,  thirty  carnation  cuttings  (White 
Enchantress)  were  planted  in  each  flat,  January  2-3,  1913.  The  flats 
were  then  placed  in  the  moist  chamber. 

The  inoculated  cuttings  began  to  die  in  about  three  weeks  (Jan- 
uary 25),  and  continued  dying  until  the  healthy  cuttings  had  rooted, 
when  the  experiment  was  discontinued  (February  11)  (Fig.  18).  The 
results  are  given  in  Table  3. 

In  most  cases  the  cuttings  inoculated  with  the  various  strains  from 
carnation  showed  a  soft,  wet,  progressive  rot  at  the  callus,  which 
extended  in  many  cases  to  the  surface  of  the  sand.  This  rot  was  very 
characteristic  of  the  attacks  of  the  carnation  strains  (Fig.  12).  At 
other  times  the  fungus  attacked  the  cuttings  just  below  the  surface 
of  the  soil,  forming  lesions  of  various  sizes  at  the  leaf  bases.  Myce- 
lium and  sclerotia  were  also  formed  along  the  stems  and  in  practically 
all  cases  between  the  leaves  just  above  the  soil. 


342 


BULLETIN  No.  ISO 


[June, 


TABLE  3. — SUSCEPTIBILITY  OF  CARNATION  CUTTINGS  TO  VARIOUS  STRAINS  OF 
EHIZOCTONIA:     EXPERIMENTS   1   AND   IA 


Strain 

Date  of 
isolation 

Number  of  plants 

Experiment  1:  1913 

Experiment  la:   1914 

Healthy)  Wilted 

Dead 

Healthy 

Wilted 

Dead 

Alfalfa  

1910 
1912 
1912 
1913 
1913 

a 

.  1913 
1911 
1911 
1911 
1911 
1911 
1912 
1912 
1912 
1912 
1913 

a 

1912 
1913 
1912 
1912 
1913 
1912 
1911 
1912 
1912 
1913 
1913 
1913 
1913 
1912 
1913 
1913 

a 

1912 
1912 
1912 

a 
a 

1912 
1913 
1912 

a 

10 
2 
3 

8 

'6 

3 
19 
6 
5 
0 
0 
1 
2 

4 
0 

0 

'6 
0 

ii 
is 

7 
4 
9 
9 
10 
16 

',3 

8 
4 

14 
2 
1 

"l 

'6 
i 
11 

0 
2 
2 
2 
3 
3 

18 
0 

0 

0 
0 

6 

12 
1 
2 
4 
7 
6 
11 

3 

18 
26 

6 
26 
26 

15 

30 
26 
0 
24 
23 
28 
28 
26 
25 

8 
30 

30 

30 
30 

io 

'6 
22 
24 
17 
14 
14 
3 

24 
4 
0 

'2 
0 
0 
33 
0 
0 

0 

3 

22 
~4 
0 
32 
0 
33 
12 
0 
0 
31 
18 
4 
14 
0 
0 
0 
0 
3 
8 
0 
34 
23 

24 
0 
34 

24 

46 

47 

.      0 
0 
0 
5 
0 
0 

'6 

0 
9 
0 
0 
o 

B 

0 
0 
0 
0 
0 
3 
0 
2 
0 
1 
0 
0 
0 
0 
0 

1 

0 
0 

2 
0 
3 
2 

'2 
1 

46 
48 
48 
10 
48 
48 

48 

45 
17 
41 

48 
14 
48 
15 
36 
48 
48 
14 
30 
42 
34 
47 
48 
48 
48 
45 
40 
47 
14 
25 

22 
48 
11 
22 

'6 
0 

Alternanthera  E.A.C.  ;  .  .  . 

'  '            E.A.F  

Amaranthus  

Aster  

Bean  

Beet  

Begonia  

Carnation  R.K  

E.O  

E.H  

E.S  

E.2  

E.F  

B.M.2  

R.107  

E.F.2  

Carrot  

Cauliflower  

Chenopodium  

Clover  

Coleus  I  

"     II  

Corn  

Cotton  I  .... 

"      II  

"      III  

Dianthus  barbatus  S.M.  . 
N.P.. 
plumarius  

sequeri  

Eggplant  I  . 

II  

Lavatera  

Lettuce  

Poinsettia  

Potato  E.P.C.  

E.P.I  

"       E.P.O  . 

"      B.Sol  

Salvia  

Sedum  

Sugar  cane  

Thistle  

Check  

}  j 

>  > 

"This  strain  had  been  in  culture  for  a  number  of  years;   the  exact  year  of 
isolation  is  not  known. 


PARASITIC  RUIZOCTONIAS  IN  AMERICA 


343 


FIG.  18. — EXPERIMENTS  1  AND  IA:  CARNATION  CUTTINGS  INFECTED  WITH  RHIZOC- 
TONIA  STRAINS  (1)  CARNATION  R.K. ;  (2)  CARNATION  R.  107;  (3)  CAR- 
NATION R.O.;  (4)  CARNATION  R.F.  (5)  BEGONIA;  (6)  COLEUS;  (7)  POIN- 
SETTIA;  (8)  SALVIA;  (9)  CAULIFLOWER;  (10)  THISTLE;  (11)  LETTUCE; 
(12)  POTATO  R.P.C.;  (13)  COTTON;  (14)  BEAN;  (15)  POTATO  R.P.O.;  (16) 
CARROT 


344  BULLETIN  No.  189  [June, 

The  percentage  of  infection  was  about  the  same  with  all  the  carna- 
tion strains  except  "Carnation  R.O.,"  which  appeared  to  have  lost 
practically  all  power  of  attacking  cuttings.  This  was  one  of  the  first 
strains  isolated  from  carnation.  Thus  the  age  of  the  strain  seemed 
to  play  an  important  role  in  its  virulence,  and  for  this  reason  the  date 
of  the  original  isolation  of  each  strain  is  included  in  the  table. 

The  strains  from  alternanthera,  coleus,  salvia,  and  poinsettia,  all 
cf  which  were  isolated  from  diseased  plants  in  the  same  cutting  bench, 
produced  in  some  cases  a  soft  wet  rot  of  the  carnation  cuttings  similar 
to  that  caused  by  the  carnation  strains.  In  the  majority  of  cases,  how- 
ever, these  strains  attacked  the  cuttings  at  the  callus,  forming  large 
browrn  sclerotia  which  covered  the  whole  callus  and  so  prevented  the 
formation  of  roots.  Brown  strands  of  the  mycelium  and  sclerotia 
were  formed  on  all  parts  of  the  cuttings  underground  and  also  be- 
tween the  leaves.  Occasionally,  small  lesions  appeared  at  the  leaf 
bases  which  were  slightly  under  the  surface  of  the  sand. 

The  two  strains  from  alternanthera  and  the  one  from  poinsettia 
killed  about  the  same  number  of  cuttings  as  the  strains  from  carna- 
tion, while  the  one  from  coleus  caused  100-percent  infection  and  rotted 
the  cuttings  off  faster  than  the  strains  from  carnation.  The  percent- 
age of  infection  with  the  strain  from  salvia  was  very  low. 

The  strain  from  begonia  produced  a  soft  rot  somewhat  different 
from  that  produced  by  the  carnation  strains.  It  appeared  on  the  stem 
at  the  surface  of  the  soil  and  sometimes  at  the  callus.  The  fungus 
formed  a  dense  mass  of  mycelium  which  completely  covered  the  sand 
beneath.  Here  again  the  virulence  was  greater  than  with  the  carna- 
tion strains,  all  the  cuttings  being  killed  and  in  a  much  shorter  time. 

The  strains  from  eggplant,  lettuce,  and  thistle  for  the  most  part 
formed  many  sclerotia  on  the  stems  and  in  between  the  leaves  of  the 
cuttings,  with  only  an  occasional  sclerotium  at  the  callus.  Small 
lesions  were  found  to  be  abundant  at  the  leaf  bases  and  on  the  stems. 
These  strains  were  very  weak,  especially  those  from  lettuce  and  thistle, 
which  had  been  in  culture  for  a  number  of  years. 

The  cuttings  infected  with  strains  from  cotton,  cauliflower,  and 
sugar  cane  rotted  off  at  the  surface  of  the  soil;  the  rot  started  as  a 
lesion  at  this  point  and  progressed  very  rapidly  until  the  cutting  was 
killed.  Smaller  lesions  were  produced  on  the  stem  underground. 
Sclerotia  and  the  brown  strands  of  the  fungus  could  be  found  in 
abundance  on  the  parts  below  the  soil.  The  strains  from  cotton  and 
cauliflower  were  very  virulent;  all  the  cuttings  inoculated  with  them 
were  killed  one  week  before  the  cuttings  inoculated  with  a  soil  culture 
of  the  carnation  strains  began  to  die  off. 

The  potato  strains,  as  a  rule,  produced  a  large  number  of  sclerotia 
and  a  dark  brown  mycelium  below  the  soil  and  on  the  leaves.  The 
percentage  of  infection  was  fairly  high  and  uniform  altho  the  average 
was  below  that  of  the  carnation  strains. 


1916]  PARASITIC  RHIZOCTONIAS  IN  AMERICA  345 

The  strains  from  alfalfa,  bean,  and  carrot  produced  symptoms  simi- 
lar to  those  from  potato.  A  large  number  of  the  cuttings  placed  in 
the  uninoculated  sand  wilted,  but  none  became  diseased. 

During  the  spring  of  1914,  beginning  on  March  7  and  ending  on 
April  7,  the  experiment  was  repeated,  the  only  difference  being  that 
a  number  of  additional  strains  were  used  and  flats  containing  forty- 
eight  cuttings  instead  of  thirty.  As  will  be  seen  in  Table  3,  the  re- 
sults were  confirmatory.  The  marked  increase  in  the  virulence  of  the 
lettuce  strain  may  have  been  due  in  part  to  the  influence  of  tempera- 
ture both  on  the  strain  and  on  the  cuttings. 

EXPERIMENTS  2  AND  2A;  INOCULATION  OF  YOUNG  CARNATION  PLANTS 
WITH  VARIOUS  STRAINS  OF  RHIZOCTONIA 

That  the  majority  of  strains  can  attack  carnation  cuttings  was 
shown  in  Experiments  1  and  la,  where  it  appeared  that  the  virulence 
of  the  strain  did  not  depend  on  the  host  from  which  it  was  originally 
isolated,  but  in  some  cases  did  depend  on  the  length  of  time  since  the 
culture  was  isolated.  To  determine  whether  rooted  plants  were  as 
susceptible  to  these  various  strains  of  Rhizoctonia  as  were  cuttings, 
further  experiments  were  carried  out :  Experiment  2  in  1913,  involv- 
ing about  400  young  plants  and  24  strains;  and  Experiment  2a  in 
1914,  in  which  about  the  same  number  of  plants  but  only  13  strains 
were  used. 

Carnation  cuttings  (White  Enchantress)  which  had  been  placed  in 
sterilized  sand  December  12,  1912,  were  planted  February  12,  1913, 
in  sterilized  flats  (9x12  inches)  containing  sterilized  soil,  fifteen  plants 
in  each  flat.  Plants  failing  to  strike  root  were  pulled  out,  leaving  an 
unequal  number  in  the  various  flats.  The  flats  were  inoculated  on 
March  23  with  250-cc.  soil  cultures  of  Rhizoctonia,  each  flat  with  a 
different  strain.  They  were  then  placed  in  a  case  in  the  greenhouse 
and  left  during  April  and  May. 

Usually  the  carnation  strains,  as  in  the  case  of  the  cuttings  (Ex- 
periments 1  and  la) ,  produced  a  soft,  wet  rot  at  the  surface  of  the  soil 
or  just  below.  On  other  plants  they  caused  small  lesions  of  various 
sizes  along  the  stems,  killing  the  plants  slowly.  Sclerotia  and  brown 
strands  of  mycelium  were  as  a  rule  present  on  plants  which  showed 
lesions  and  on  others  less  badly  diseased. 

Only  an  occasional  plant  in  the  flats  infected  with  other  strains 
than  carnation  developed  a  soft,  wet  rot.  In  the  majority  of  cases 
where  infection  took  place  the  strains  produced  lesions  of  various  sizes 
on  the  stems  at  the  surface  of  the  soil  or  just  below,  slowly  killing  the 
plants  (Fig.  13).  As  a  rule,  sclerotia  and  mycelium  were  also  present 
on  the  stems  of  the  infected  plants.  The  plants  in  the  check  flat  re- 
mained healthy. 


346 


BULLETIN  No.  189 


[June, 


The  resistance  of  the  rooted  carnation  plants  to  the  fungus,  as 
shown  in  Table  4,  was  much  more  marked  than  with  the  cuttings.  In 
the  few  exceptions  the  fungus  appeared  able  to  infect  the  plants  al- 
most as  readily  as  it  had  the  cuttings. 

In  1914  this  experiment  was  essentially  repeated.  Thirty  young  car- 
nation plants  (Rosette)  were  placed  in  each  of  a  number  of  flats 
(12x18  inches) .  On  April  26,  after  the  plants  were  rooted,  some  of  the 
old  infected  sand  from  the  inoculated  flats  used  in  Experiment  la  was 
mixed  with  the  soil  in  which  the  plants  were  growing.  The  experiment 
was  continued  until  June  1.  The  results,  which  are  presented  in 
Table  4,  were  similar  to  those  of  Experiment  2.  As  in  that  experiment, 
the  plants  in  the  check  flat  remained  healthy,  with  the  exception  of 
two  that  wilted  and  died  from  attacks  of  a  Fusarium. 

TABLE  4. — SUSCEPTIBILITY  OF  YOUNG  ROOTED  CARNATION  PLANTS  TO  VARIOUS 
STRAINS  OF  RmzocTONrA:  EXPERIMENTS  2  AND  2A 


Strain 

Number  of  plants 

Experiment    2:    1913 

Experiment    2a:    1914 

Total  {Healthy]    Dead 

Total 

Healthy)  Dead 

Alternanthera    R  A.C  

15  - 
15 

12 
5 

ii 

2 

'i 

6 
2 
0 
2 
4 

13 
9 
9 

2 
8 
10 

'G 

13 

15 
7 
8 
10 

13 
12 
15 

3 

10 

'i 

12 

is 

7 
12 
15 
12 
11 

2 
6 
6 
13 

7 
4 

-9 

'2 

0 
7 
6 
5 

2 
2 
0 

30 
30 
30 

30 

30 

30 

30 
30 
30 

30 
30 

30 

30 
SO 

is 

25 
20 

is 

is 
io 

22 
23 
13 

12 
24 
19 

24 

28 

12 
5 
10 

15 

15 

20 

's 

7 
17 

18 
6 
11 

'6 
'JJ- 

"              R.A.F  

Amaranthus    

Beet   

Begonia     

15 
14 

Carnation  R  »K  

R.H  

R.S  

14 
13 
14 
15 
14 
15 

15 
15 
15 
15 
15 
14 

15 

15 
15 
14 
14 
15 

15 
14 
15 

R.2  

R.F  

R.F  

R.M.2  

R.107  

R.F.2  

Carrot    

Cauliflower     

Coleus  I    

Cotton  I   

"       II    

"       III    

Dianthus  barbatus  N.P  

Efjtmlant  I  . 

Lavatera   

Lettuce    

Potato  R.P.C  

"       R.P.I  

"       R.P.O  

Salvia    

Sedum    

Sugar  cane  

Thistle     

Check     

» 

"Killed  by  Fusarium. 


1916] 


PARASITIC  RHTZOCTONIAS  IN  AMERICA 


347 


EXPERIMENT  3:     INOCULATION  OF  OLD  CARNATION  PLANTS  IN  POTS 
WITH  VARIOUS  STRAINS  OF  RHIZOCTONIA 

The  resistance  of  young  rooted  carnation  plants  to  the  various 
strains  of  Rhizoctonia  other  than  those  from  carnation  was  very 
marked  in  Experiments  2  and  2a.  To  determine  whether  or  not  old 
carnation  plants  were  even  more  resistant,  the  following  experiment 
was  carried  out,  involving  90  plants  and  18  strains. 

Carnation  plants  (White  Enchantress  and  White  Perfection) 
were  brought  in  from  the  field  and  planted  in  pots,  which  were  then 
placed  in  the  bench.  The  plants  were  grown  under  the  best  possible 
cultural  conditions  and  on  November  27,  1912,  when  they  had  become 
firmly  established,  they  were  inoculated.  Five  plants  of  the  same  size 
were  used  for  each  test,  one  being  left  as  a  check.  The  other  four  were 
inoculated  by  placing  a  bit  of  infected  green-bean  plug  near  the  stem 
about  one-half  inch  below  the  surface  of  the  ground.  The  stems  of 
two  plants  of  each  test  were  slightly  wounded  before  the  plugs  were 
placed  by  them.  Observations  were  discontinued  on  March  27,  four 
months  later.  The  results  are  presented  in  Table  5. 

Only  two  plants  inoculated  by  contact  died  during  the  course  of 
the  experiment,  and  both  were  killed  by  carnation  strains.  However, 
where  the  stem  was  slit,  the  various  strains  were  in  most  cases  able  to 
infect  and  kill  the  plant.  The  check  plants  remained  healthy  during 
the  experiment. 

TABLE  5. — SUSCEPTIBILITY  OP  OLD  CARNATION  PLANTS    (IN  POTS)    TO  VARIOUS 
STRAINS  OP  RHIZOCTONIA:  EXPERIMENT  3 


Strain 

Plants  inoculated  by 

Check  plants 

Contact 

Slit 

Healthy  I  Diseased 

Healthy 

Diseased 

Healthy  I  Diseased 

Alternanthera  R.A.F  

2 
2 
2 
2 
1 
1 
2 

2 
2 
2 
2 
2 
2 
2 
2 
2 
2 

0 
0 
0 
0 

1 
1 

0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 

1 

0 
0 
0 
0 
0 
0 

1 

.      0 
2 
1 
0 
0 
0 
0 
1 
0 
0 

1 

2 

2 
o 

2 
2 
2 
1 
2 
0 
1 
2 
2 
2 
2 
1 
2 
2 

1 
1 
1 
1 
1 
1 
1 
1 
1 
1 
1 
1 
1 
1 
1 
1 
1 
1 

0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 

Carnation   R.K  

R.O  

R.H  

R.S.     

R.2      

R.F  

R.M.2    

R.107    

Carrot     

Cotton  II     

Eggplant  I   

Lettuce     

Poinsettia  

Potato  R.  Sol  

"       R.P.O  

"       R.P.I  

Thistle    . 

348 


BULLETIN  No.  189 


[June, 


EXPERIMENT  4:     INOCULATION  OF  YOUNG  CARNATION  PLANTS  WITH 
ISOLATED  AND  WITH  REISOLATED  STRAINS  OF  RHIZOCTONIA 

The  object  of  Experiment  4  was  to  compare  the  virulence  of  various 
strains  of  Rhizoctonia  when  they  were  inoculated  on  carnation  plants 
for  the  first  time,  and  after  they  had  been  inoculated  on  carnation 
and  reisolated.  Fifteen  strains,  taken  at  random,  and  about  300  plants 
were  used. 

On  December  12,  1912,  a  number  of  carnation  cuttings  were  made 
and  placed  in  sterilized  sand.  They  were  allowed  to  remain  in  the 
sand  until  well  rooted.  On  March  22,  when  the  plants  were  from 
four  to  six  inches  high  and  breaking  nicely,  they  were  placed  in  three- 
inch  pots  in  sterilized  soil.  They  were  then  inoculated  by  placing  a 
bit  of  bean  pod  infected  with  Rhizoctonia  near  the  stem  just  below  the 
surface  of  the  soil.  Table  6  gives  the  results  obtained. 

With  seven  strains  the  virulence  of  the  reisolated  fungus  was 
slightly  greater  than  that  of  the  original  isolation.  With  two  it  was 
slightly  less. 

TABLE  6. — COMPARATIVE   VIRULENCE  OF  ISOLATED   AND  EEISOLATED  STRAINS  OP 
EHIZOCTONIA  WHEN  INOCULATED  ON  YOUNG  CARNATION  PLANTS  (IN  POTS)  : 

EXPERIMENT  4 


Strain 

Original  isolation 

Reisolation 

Healthyl  Diseased 

Healthy!  Diseased 

Bean           

9 
6 

1 
4 

*5 
4 

0 
3 

"(5 

6 
0 

1 
0 
1 
0 
0 
0 
0 

9 
1 
1 
2 
(5 
7 
4 
3 
7 
5 
10 
7 
10 
8 
9 

1 

9 
9 
8 
5 
3 
6 
7 
3 
5 
0 
3 
0 
2 
1 

Carnation  B.K  

R.K  

E.H  

5 
G 
10 

7 

R  S  

R2      

R.F  

R  F 

R.M.2  

4 
4 
10 
9 
10 
9 
10 
10 
10 
10 

R.107  

Cauliflower     

Cotton  I  

"       n  

Potato  RPI                                

Sugar  cane        

Check    

>  > 

'  '                                                      • 

EXPERIMENT  5:     INOCULATION  OF  OLD  CARNATION  PLANTS  IN  THE 
BENCH  WITH  VARIOUS  STRAINS  OF  RHIZOCTONIA 

Experiment  5  was  similar  to  the  preceding  experiment  except  that 
the  carnation  plants  used  were  older  and  were  grown  in  the  bench  in- 
stead of  in  pots,  and  that  inoculations  were  made  with  only  eight 
strains  of  Rhizoctonia,  chosen  at  random. 


1916}  PARASITIC  KHIZOCTONIAS  IN  AMERICA  349 

On  September  1,  1913,  the  soil  in  two  five-foot  sections  in  the  green- 
house was  sterilized,  and  twenty  carnation  plants  from  the  field  were 
placed  in  each  section,  four  plants  in  a  row.  Four  rows  in  each  sec- 
tion were  each  inoculated  with  a  different  strain  of  Ehizoctonia,  by 
means  of  pieces  of  infected  bean  plugs.  The  middle  row  in  each  sec- 
tion was  left  as  a  check. 

The  plants  began  to  die  off  at  the  end  oi  three  weeks  and  con- 
tinued dying  until  the  close  of  the  experiment,  October  31.  They  all 
died  in  a  manner  characteristic  of  stem  rot.  All  the  strains  used 
proved  to  be  virulent  except  the  one  from  beet  (see  Table  7).  The 
check  plants  remained  healthy  thruout  the  experiment. 

TABLE    7. — SUSCEPTIBILITY   OP    OLD   CARNATION    PLANTS    (IN   THE    BENCH)    TO 
VARIOUS  STRAINS  OF  EHIZOCTONIA:  EXPERIMENT  5 

Strain  ]Healthy  |  Diseased 


Beet  

3 

1 

Carnation  R.107  

0 

4 

Cauliflower  

1 

3 

Cotton  II  

0 

4 

Dianthus  barbatus  S.M  

1 

3 

plumarius   .                                                   

0 

4 

Eggplant  I  .•  

1 

3 

Potato  B.  Sol  

1 

3 

Check   

4 

0 

7  > 

4 

0 

The  high  mortality  of  the  strains  in  this  experiment  was  due,  to  a 
large  extent,  to  the  date  of  inoculation.  The  plants  in  the  preceding 
experiments  were  inoculated  either  late  in  the  fall  or  in  the  early 
spring,  when  the  temperature  in  the  greenhouse  was  low  and  normal 
and  not  influenced  by  outside  conditions.  The  temperature  in  the 
house  during  September  and  October,  when  these  plants  were  inocu- 
lated, is  very  high ;  hence  the  virulence  of  the  fungus  was  much  greater. 
The  effects  of  inoculating  plants  at  various  times  of  the  year  are 
clearly  brought  out  in  the  next  experiment. 

EXPERIMENT  6 :     INOCULATION  OF  CARNATION  PLANTS  WITH  Rmzoc- 
TONIA  AT  DIFFERENT  TEMPERATURES 

During  the  season  1913-14  a  number  of  sections  containing  carna- 
tions were  reserved  in  the  greenhouse,  and  at  different  times  of  the 
year  the  plants  were  inoculated  with  RMzoctonia  from  carnation. 
This  experiment  was  for  the  purpose  of  ascertaining  the  relative 
virulence  of  Rhizoctonia  when  inoculated  on  carnation  plants  at  dif- 
ferent temperatures. 

Each  section  contained  twenty  plants,  sixteen  of  which  were  in- 
oculated by  placing  infected  bean  plugs  at  the  base  of  the  stem.  The 
remaining  four  plants  served  as  checks. 


350 


BULLETIN  No.  189 


[June, 


TABLE    8. — RELATIVE    VIRULENCE    OF    EHIZOCTONIA    INOCULATED    ON    CARNATION 
PLANTS  AT  DIFFERENT  TEMPER  \TURES:    EXPERIMENT   6 


Section 

Date  of 
inoculation 

Experiment 
discontinued 

Inoculated   plants 

Check  plants 

Healthy 

Diseased 

Healthy  1  Diseased 

143 

Sept.    1,  1913 

Oct.       1,  1913 

1 

15 

4 

0 

140 

Oct.      1,  1913 

Nov.     1,  1913 

3 

13 

4 

0 

139 

Nov.     1,  1913 

Jan.      1,  1914 

10 

6 

4 

0 

138 

Dee.      1,  1913 

Feb.      1,  1914 

8 

8 

4 

0 

137 

Jan.      1,  1914 

Mar.     1,  1914 

14 

2 

4 

0 

134 

Feb.      1,  1914 

Apr.      1,  1914 

3 

13" 

4 

0 

133 

Mar.     1,  1914 

May      1,  1914 

12 

4 

4 

0 

132 

Apr.      1,  1914 

June     1,  1914 

9 

7 

4 

0 

131 

May     1,  1914 

July      1,  1914 

0 

16 

4 

0 

130 

June    1,  1914 

July      1,  1914 

2 

14 

4 

0 

128 

July     1,  1914 

July  23,   1914 

6 

10 

4 

0 

•Ten  plants  found  infected  April  1;  only  three  plants  died  during  the  months 
of  February  and  March. 

As  can  be  seen  from  Table  8,  the  death  rate  of  the  plants  inocu- 
lated on  September  1  and  October  1  was  almost  100  percent.  This 
rate  diminished  very  markedly  when  the  plants  were  inoculated  later 
in  the  season,  increasing  with  the  plants  inoculated  during  the  spring 
months  until  with  those  inoculated  on  May  1,  it  had  again  reached  a 
high  percentage.  This  condition  prevailed  during  the  summer  months, 
showing  very  noticeably  the  influence  of  temperature  on  mortality. 

EXPERIMENT  7:    INOCULATION  OF  VARIOUS  HOSTS  (SEEDLINGS)  OTHER 
THAN  CARNATION  WITH  VARIOUS  STRAINS  OF  RHIZOCTONIA 

In  the  preceding  experiments  all  the  work  was  carried  on  with 
carnation  plants  of  different  ages.  It  was  found  that  under  certain 
conditions  all  the  strains  used  could  attack  these  plants,  but  that  the 
resistance  was  somewhat  increased  when  the  plants  were  rooted.  To 
determine  whether  the  same  results  could  be  obtained  with  other 
plants,  a  number  of  further  experiments  were  made. 

Small  flats  (8x10  inches)  were  disinfected  and  filled  with  a  mix- 
ture of  sterilized  sand  and  soil  suitable  for  germinating  seed.  In  each 
flat  a  250-cc.  soil  culture  of  one  of  the  various  strains  used  was  thoroly 
mixed  with  the  soil,  and  the  whole  allowed  to  stand  for  several  days. 
The  seeds,  after  a  short  soaking  in  formalin  (1-150),  were  sown  in  the 
flats,  thirty-one  in  all,  care  being  taken  not  to  plant  them  too  closely. 
Nine  different  kinds  of  seedlings  and  13  strains  wrere  used  in  the  ex- 
periment. The  results  obtained  are  given  in  Table  9. 

In  the  first  group  of  the  various  hosts,  clover  proved  to  be  more 
resistant  than  alfalfa,  while  the  injury  to  corn  roots  was  negligible. 
Of  the  different  strains,  the  one  from  clover  proved  the  most  virulent, 
while  the  one  from  corn  was  the  weakest  (Fig.  19). 


1916] 


PARASITIC  EHIZOCTONIAS  IN  AMERICA 


351 


TABLE  9.- 


-SUSCEPTIBILITT  OF  VARIOUS  PLANTS    (SEEDLINGS)    OTHER  THAN   CARNA- 
TION TO  VARIOUS  STRAINS  OF  KHIZOCTONIA:  EXPERIMENT  7 


Group  1 


Strain 

On  clover 

On  alfalfa 

On  corn 

Olov6r        

150  seeds 

150  seeds 

30  seeds 

Most  of  seedlings 
killed  at  germina- 
tion; 6  came  up; 
5  infected  below 
surface  of  ground, 
showing  lesions  ; 
1  healthy 

All  seeds  attacked 
by  fungus  at  ger- 
mination. Ehizoc- 
tonia present  in 
seeds 

Plants  4-6  inches 
high.  Seed  in  all 
cases  showed  the 
presence  of  Bhi- 
zoctonia,  but 
whether  it  would 
kill  the  whole 

Alfalfa              .... 

Abbut     15     percent 

80    percent    damped 

plant  is  a  ques- 

damped off  in  typ- 
ical manner.  Le- 
sions at  surface  of 
ground 

off.  Others  in  va- 
rious stages  of  in- 
fection. 5  percent 
healthy 

tion.  However, 
fungus  is  able  to 
live  in  the  roots 
of  the  corn.  Cul- 

Carnation R.  107.  . 

Only  few  plants 
infected.  First 
leaves  of  a  large 
number  dead  from 
effects  of  fungus 

70  percent  damped 
off.  Condition  sim- 
ilar to  that  of 
plants  inoculated 
with  alfalfa  strain 

tures  of  Ehizoc- 
tonia were  ob- 
tained from  the 
seeds 

Corn 

2     percent     damped 

8     percent     damped 

off.  Ehizoctonia 
present  on  the 
roots  of  living 
plants,  but  did  not 
seem  virulent 

off.  Eemaining 
plants  healthy 

Group  2 


Strain 

On  lettuce 

On  eggplant 

On  cabbage 

Lettuce    

150  seeds 

150  seeds 

90  percent  damped 
off.  Lesions  on 
stem  at  surface 
of  ground.  Leaves 
also  attacked, 
causing  a  rot 

2     percent     damped 
off.       Lesions     at 
surface  of  ground. 
Typical 

Eggplant  I  

75    percent    damped 

3—4  percent  damped 

off.  Lesions  typi- 
cal, like  lettuce 

off.  Typical 

Thistle  

(50    percent    damped 

5     percent     damped 

off.  Lesions  typi- 
cal, like  those  ori 
plants  inoculated 
with  eggplant 
strain.  Action  of 
fungus  slower  but 
virulent 

off.  Small  circular 
lesions        present. 
Typical 

Carnation  E.F  

60  percent  damped 
off.  Like  thistle  ; 
slower  in  effect, 
but  still  virulent 

All  healthy 

40  percent  infected. 
Lesions  in  form 
of  a  collar 
around  stem  at 
surface  of  ground 

Cauliflower    

3     percent     damped 

Only         3         plants 

off.  Typical  le- 
sions 

healthy.  Seedlings 
attacked  at  ger- 
mination 

352 


BULLETIN  No.  189 
TABLE  9. — Concluded 


[June, 


Group  3 


Strain 

On   radish 

On    turnip 

On  beet 

Radish     

150   seeds 

150   seeds 

1  percent  infected 
at  base  of  stems. 
Several  completely 
rotted 

Seedlings  attacked 
at  germination. 
Only  2  healthy 
plants 

Potato  R.P.C.    .  .  . 

15    percent  infected 

at  base  of  stems 
where  root  begins. 
Small  wounds  like 
potato  scab  due 
to  Rhizoctonia 

off.  Some  rotted 
off  at  the  ground 

Carrot    

Seedlings      attacked 

50  percent  infected 

at  germination. 
Only  3  healthy 
plants 

All  showed  collar 
rot.  Some  rotted 
off 

Carnation  R.F.    .  . 

50  percent  infected. 
Lesions  at  base  of 
stems.  Few  rotted 
off 

98  percent  damped 
off.  Showed  collar 
rot.  Typical 

FIG.  19. — EXPERIMENT  7 :  UPPER  Row :  ALFALFA  SEEDLINGS  INFECTED  WITH 
RHIZOCTONIA  STRAINS  (1)  CLOVER;  (2)  ALFALFA;  (3)  CARNATION  R.  107! 
(4)  CORN.  LOWER  Row:  LETTUCE  SEEDLINGS  INFECTED  WITH  RHIZOCTONIA  STRAINS 
(1)  LETTUCE;  (2)  EGGPLANT  I;  (3)  THISTLE;  (4)  CARNATION  R.F. 

Of  the  seedlings  in  the  second  group,  lettuce  and  cabbage  were 
quite  susceptible ;  eggplant  seedlings  were  very  resistant.  The  strain 
from  cauliflower,  altho  it  caused  only  a  slight  damping-off  of  lettuce 


1916]  PARASITIC  EHIZOCTONIAS  IN  AMERICA  353 

seedlings,  produced  practically  100-percent  infection  in  the  case  of 
cabbage  seedlings  (Fig.  19). 

In  the  third  group,  beet,  radish,  and  turnip  seedlings  proved  very 
susceptible  to  damping-off  of  Rhizoctonia.  It  is  rather  interesting  to 
observe  that  while  the  strain  from  radish  was  able  to  cause  only 
1-percent  infection  of  radish  seedlings,  it  caused  almost  100-percent 
infection  of  turnip  seedlings. 

Taking  the  experiment  as  a  whole,  it  is  seen  that  a  great  variation 
exists  in  susceptibility  of  seedlings  and  in  virulence  of  strains.  It  is 
clear  that  under  certain  conditions  all  the  strains  can  attack  a  given 
host  with  about  the  same  virulence. 

EXPERIMENT  8:    INOCULATION  OF  VARIOUS  HOSTS  (OLD)  OTHER  THAN 
CARNATION  WITH  VARIOUS  STRAINS  OF  RHIZOCTONIA 

In  Experiment  8  the  preceding  experiment  was  carried  one  step 
farther,  older  plants  being  used  rather  than  seedlings.  A  number  of 
plants  were  taken  from  flats  while  small  and  transplanted  to  four-inch 
pots,  where  they  were  allowed  to  grow  for  about  two  months.  The 
soil  in  these  pots  was  not  sterilized.  Each  plant,  with  the  exception  of 
the  check  plants,  was  inoculated  by  placing  an  infected  bean  plug  in 
contact  with  it  just  below  the  surface  of  the  soil.  Four  kinds  of 
plants,  50  of  each,  and  12  strains  were  employed.  The  observations 
from  this  experiment  are  recorded  in  Table  10. 

In  Group  1,  the  tomato  plants  proved  resistant  to  the  attacks  of 
the  various  strains,  with  the  exception  of  the  one  from  carnation,  which 
produced  a  slight  infection  on  two  plants.  In  the  case  of  the  cabbage 
plants,  the  strains  from  cotton  and  from  cauliflower  exhibited  a  marked 
specialization,  producing  50-  and  90-percent  infection,  respectively,  on 
these  plants,  while  on  tomato  plants  they  produced  no  infection  what- 
ever. Cabbage  was  the  only  host  in  the  experiment  susceptible  to  all 
the  strains  with  which  it  was  inoculated. 

The  carnation  strains  in  Groups  2  and  3  also  proved  more  virulent 
than  the  other  strains,  producing  50-percent  infection  on  lettuce  and 
100-percent  infection  on  beet  (Fig.  9).  Of  the  other  strains,  eggplant 
alone  was  able  to  attack  the  plants,  producing  a  slight  infection  on 
two  lettuce  plants. 

EXPERIMENT  9:     INOCULATION  OF  VARIOUS  HOSTS  (CUTTINGS,  SEED- 
LINGS, AND  LARGER  PLANTS)  WITH  VARIOUS  STRAINS  OF  RHIZOCTONIA 

The  kinds  of  plants  used  in  the  foregoing  experiments  were  some- 
what limited.  Increased  facilities  being  at  hand  in  the  spring  of  1914, 
a  more  extensive  series  of  inoculations  was  made  with  cuttings,  seed- 
lings, and  larger  plants  of  various  kinds.  In  all,  about  350  cuttings, 
3.000  seedlings,  and  300  larger  plants  were  inoculated.  Thirty-two 
strains  of  Rhizoctonia  were  used. 


354 


BULLETIN  No.  181) 


[June, 


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1916]  PARASITIC  RHI/.OCTONIAS  IN  AMERICA  355 

Flats  (9x12  inches)  were  infected  as  in  Experiment  7,  and  a  vary- 
ing number  of  cuttings,  seeds,  and  plants  placed  in  them  on  March  7, 
1914.  Pure  cultures  from  the  diseased  plants  in  each  flat  were  made, 
and  Rhizoctonia  was  isolated  in  each  case.  Following,  the  results  of 
the  experiment  are  taken  up  in  detail. 

"  Alternanthera  E.A.C."  on  Alternanthera. — 48  cuttings.  On  March  18  all 
were  dead.  The  infection  was  first  noticed  as  a  small,  brown  lesion  on  one  side 
at  the  surface  of  the  ground;  later  the  lesion  girdled  the  whole  stem.  The  fun- 
gus also  attacked  the  cut  surface  of  the  cutting,  causing  a  lesion  and  in  some 
instances  a  slow,  wet  rot.  The  mycelium,  which  grew  very  profusely,  attacked 
the  leaves,  producing  a  characteristic  rot. 

"Alternanthera  E.A.F."  on  Alternanthera. — 48  cuttings.  The  experiment 
was  carried  out  exactly  like  the  above  and  produced  the  same  results. 

"Alternanthera  E.A.F."  on  Gernanium. — 48  cuttings.  These  were  planted 
March  20  in  the  infected  flat  in  which  alternanthera  cuttings  had  died.  By 
May  2,  42  of  them  were  rotted  while  6  were  rooted  and  healthy. 

"Amaranthus"  on  Amaranthus  salicifolius. — 100  seeds.  Seeds  germinated 
March  23,  and  by  April  1  all  the  plants  in  the  flat  damped  off  in  a  character- 
istic manner. 

"Aster"  on  Aster. — 100  seeds.  Seeds  germinated  March  18  and  a  few  be- 
gan immediately  to  damp  off.  By  April  1,  29  percent  had  died,  while  the  others 
remained  healthy. 

"Bean"  on  Bean. — 30  seeds.  Seeds  germinated  March  19,  and  after  two 
months  only  5  percent  were  killed  by  the  fungus.  . 

"Beet"  on  Beet. — 100  seeds.  Seeds  germinated  March  19  and  began  to 
damp  off.  About  25  percent  damped  off  and  later  about  25  percent  more  be- 
came scabby  because  of  the  formation  of  small,  depressed  lesions.  Injury  here 
was  similar  to  the  infection  of  beet  by  the  strains  from  carnation. 

' '  Carnation ' '  on  Bean. — 50  plants.  On  May  8,  bean  plants  about  three 
inches  high  were  transplanted  from  flats  to  infected  sections  (Nos.  157  and 
173).  The  plants  took  hold  readily,  and  after  about  two  weeks  began  to  show 
signs  of  infection.  The  disease  progressed  rather  slowly ;  most  of  the  plants 
produced  a  few  pods  before  they  were  killed  by  the  fungus.  When  pulled  up, 
May  19,  every  one  was  diseased  or  dead  (Fig.  8).  A  detailed  description  of 
four  typically  infected  bean  plants  follows.  It  will  be  seen  that  it  corresponds 
in  most  details  to  the  descriptions  given  by  Barrus,9  Fulton,45  and  Hedgcock60 

Plant  No.  1:  Three  distinct  lesions  were  present,  one  directly 
above  the  other  on  the  stem.  Lesions  were  oval  in  shape  with  a  reddish 
brown  band  surrounding  a  lighter  colored  sunken  area.  Evidences  were 
present  of  young  lesions  over  the  entire  stem  and  larger  roots  under- 
ground. The  wounds  extended  beneath  the  cortical  layer  to  the  woody 
tissue. 

Plant  No.  2:  Eoots  were  infected  at  the  joint  of  their  union  with 
the  main  stem.  The  lateral  root  was  very  badly  infected  and  rotted  off 
entirely.  The  lesions  on  the  smaller  roots  were  small,  depressed,  and  of 
a  reddish  brown  color. 

Plant  No.  3:  A  large,  reddish  brown  lesion  extended  from  the  sur- 
face of  ground  downward  2.5  centimeters.  Spots  were  sunken  and  ex- 
tended thru  the  cortex  to  woody  tissue  beneath.  Two  small  sunken  areas 
of  a  reddish  brown  color  were  present  on  the  stem  one  inch  above  the  sur- 
face of  the  ground. 

Plant  No.  4 :  A  large,  depressed,  reddish  brown  area  extended  from 
the  surface  of  the  ground  downward  2.5  to  3  centimeters,  almost  encircling 
the  stem.  Cortical  tissue  rotted  away  exposing  the  woody  tissue  beneath. 

"Carnation"  on  Beet. — 30  plants.  On  May  8,  young  beet  plants  were  trans- 
planted to  a  section  (No.  158)  infected  with  Rhizoctonia  from  carnation.  By 


356  BULLETIN  No.  189  [June, 

May  20  they  all  showed  some  scab.  A  number  were  infected  at  the  crown,  where 
a  large  number  of  leaves  were  completely  cut  off  at  the  base  by  the  fungus.  Sev- 
eral beets  had  depressed  lesions  which  extended  deep  into  the  tissues. 

"Carnation"  on  Cabbage. — 25  plants.  On  May  8,  young  cabbage  plants 
were  transferred  from  flats  to  a  section  (No.  163)  in  the  greenhouse  infected 
with  a  soil  culture  of  Khizoctonia  from  carnation.  Some  of  these  plants  grew 
to  maturity,  but  when  they  were  pulled  up,  May  21,  the  stems  and  roots  were  cov- 
ered with  black,  depressed  lesions  (Fig.  11).  Ninety  percent  of  the  plants  set  in 
the  bench  were  infected  in  this  way.  Where  the  leaves  touched  the  soil  the  fun- 
gus caused  a  slow,  wet  rot. 

' '  Carnation ' '  on  Carrot. — 50  plants.  Carrot  plants  were  transferred  on 
May  8  from  flats  to  an  infected  section  (No.  158)  in  the  greenhouse.  By  May 
21  only  a  few  had  rotted.  The  rot  started  at  the  crown,  where  the  petioles  were 
attacked,  and  worked  down  into  the  tissues  of  the  root  and  up  into  the  leaves. 
The  rot  from  the  crown  goes  into  the  interior  of  the  root,  and  thus  the  root  does 
not  show  any  signs  of  rot  on  the  outside  for  some  time.  Occasionally  lesions 
were  found  on  the  sides  of  the  carrots  and  on  the  larger  roots  where  they  branched 
from  the  fleshy  part. 

"Carnation"  on  Corn. — 10  seedlings.  Corn  seedlings  about  8  inches  tall 
were  transplanted  on  May  8  from  flats  to  an  infected  section  (No.  153)  in  the 
greenhouse.  The  plants  grew  to  maturity.  When  pulled  up,  only  small  lesions 
were  to  be  found  on  the  roots.  These  were  only  slightly  depressed  and  did  not 
retard  the  growth  of  the  plant. 

"Carnation"  on  Eggplant. — 25  plants.  On  May  8,  eggplants  were  trans- 
ferred to  an  infected  section  in  the  greenhouse  (No.  170).  The  plants  reached 
maturity  with  no  loss.  When  they  were  pulled  up,  no  infection  was  to  be  found. 

"Carnation"  on  Lettuce. — 60  plants.  On  March  16,  lettuce  plants  were 
transferred  to  an  infected  section  (No.  153).  By  March  24,  16  percent  of  the 
plants  were  killed.  No  more  loss  occurred  and  the  plants  were  cut  on  April  21. 

"Carnation  B.  107"  on  Cabbage. — 100  seeds.  Seeds  germinated  March  19 
and  began  to  damp  off  immediately.  By  May  21  those  which  did  not  damp  off 
were  infected  in  various  ways.  Some  had  constrictions  just  at  the  surface  of  the 
soil;  others  had  definite  lesions  along  the  stern  and  larger  roots.  Where  the  plants 
were  crowded,  spots  of  various  sizes  were  formed  on  the  lower  leaves  which  touched 
the  soil. 

' '  Carnation  E.M.2 ' '  on  Carrot. — 150  seeds.  Seeds  germinated  March  18. 
When  the  experiment  was  discontinued,  May  21,  only  10  percent  of  the  carrots 
were  infected  at  the  crown.  One  showed  a  constriction  which  was  quite  marked. 

"Carnation  R.F."  on  Beet. — 100  seeds.  Seeds  germinated  March  16  and 
began  to  damp  off  immediately,  so  that  by  March  24,  40  percent  of  the  plants 
were  dead.  The  remainder,  when  examined  on  May  21,  were  all  more  or  less 
scabby.  Some  were  rotted  at  the  crown. 

' '  Carnation  E.F.2 ' '  on  Bean. — 30  seeds.  Seeds  germinated  March  19.  When 
the  experiment  was  discontinued,  May  8,  but  slight  infection  could  be  noticed. 

"Carrot"  on  Carrot. — 150  seeds.  Seeds  germinated  March  16.  By  May  21 
only  a  few  of  the  carrots  were  infected.  An  occasional  plant  showed  crown  rot, 
which  was  especially  noticeable  at  the  base  of  the  leaves. 

"Cauliflower"  on  Cabbage. — 100  seeds.  Seeds  germinated  March  13.  A  few 
seedlings  began  to  damp  off  March  14  and  by  May  21  most  of  the  plants  were 
infected.  Lesions  could  be  found  on  the  stems,  occasionally  one  girdling  the  whole 
stem  and  forming  a  sort  of  constriction  as  the  plant  developed.  A  number  of 
spots  varying  in  size  could  also  be  found  on  the  lower  leaves  which  touched  the 
soil. 

"Chenopodium"  on  Alfalfa. — 100  seeds.  Seeds  germinated  March  13.  Two 
weeks  later  60  percent  of  the  seedlings  had  damped  off  in  a  characteristic  manner. 

"Clover"  on  Clover. — 150  seeds.  Seeds  germinated  March  12  and  began 
to  damp  off  slowly.  By  March  21,  however,  the  plants  had  reached  sufficient 
size  so  that  no  more  damping-off  occurred.  In  all  about  10  percent  of  the  seed- 
lings were  diseased. 


1916]  PARASITIC  BHIZOCTONIAS  IN  AMERICA  357 

"Coleus  I"  on  Coleus. — 100  seeds.  The  seeds  were  all  killed  by  the  fun- 
gus as  they  were  germinating. 

"Coleus  I"  on  Coleus. — 48  cuttings.  By  March  18  all  the  cuttings  had 
rotted  off.  Infection  began  as  small  spots  at  the  surface  of  the  ground  or  at 
the  callus.  Underground  lesions  of  all  sizes  were  produced,  from  small  spots  to 
places  where  the  whole  stem  was  girdled.  The  leaves  of  the  cuttings  were  over- 
run with  mycelium,  the  fungus  in  many  cases  rotting  them  off. 

"Coleus  II"  on  Chrysanthemum. — 48  cuttings.  The  old  infected  flat  in  which 
the  coleus  cuttings  had  rotted  off  was  planted  to  chrysanthemum  cuttings  March 
20.  By  March  27  all  of  them  had  rotted  off  at  the  surface  of  the  ground.  In 
some  a  soft,  wet  rot  was  produced. 

"Coleus  II"  on  Coleus. — 100  seeds.  Seeds  germinated  March  24  and  began 
to  damp  off  slowly.  By  May  21  only  30  percent  of  the  plants  were  still  healthy. 

"Coleus  II"  on  Coleus. — 48  cuttings.  All  cuttings  rotted  off  as  with  "Coleus 
I. ' '  The  red-colored  cuttings  rotted  off  faster  and  were  much  more  susceptible 
than  those  of  the  green  variety. 

"Corn"  on  Corn. — 50  seeds.  Seeds  germinated  March  17.  The  plants  grew 
to  maturity.  When  pulled  up,  no  signs  of  infection  were  noticed. 

"Cotton  I"  on  Cotton. — 50  seeds.  The  fungus  caused  a  rotting  of  the  seeds 
as  they  germinated. 

"Cotton  III"  on  Cotton. — 50  seeds.    Eesults  same  as  preceding. 

"Dianthus  barbatus  S.M."  on  Dianthus  barbatus  (Sweet  William). — 100 
seeds.  Seeds  germinated  March  19  and  began  to  damp  off  immediately.  By  May 

22,  50  percent  of  the  seedlings  were  diseased. 

"Dianthus  barbatus  N.  P."  on  Dianthus  barbatus  (Sweet  William). — 100 
seeds.  Eesults  same  as  preceding. 

' '  Dianthus  plumarius ' '  on  Dianthus  plumarius. — 100  seeds.  Seeds  germinated 
March  14.  By  May  22,  80  percent  of  the  plants  had  damped  off. 

"Dianthus  sequeri"  on  Dianthus  sequeri. — 100  seeds.  Seeds  germinated 
March  18  and  began  to  damp  off  immediately.  By  May  22  only  about  25  percent 
were  still  healthy. 

"Eggplant  I"  on  Eggplant. — 150  seeds.  Seeds  germinated  March  23.  By 
May  8  only  3  to  4  percent  of  the  plants  had  damped  off. 

"Eggplant  II"  on  Eggplant. — 150  seeds.  Seeds  germinated  March  23.  The 
fungus  caused  a  rot  of  the  seeds  at  germination. 

"Lavatera"  on  Lavatera  trimestris. — 100  seeds.  Seeds  germinated  March 
12.  By  May  22  about  25  percent  of  the  seedlings  had  damped  off  (Fig.  14).. 
On  the  remainder,  lesions  of  various  sizes  were  present,  which  in  some  cases  girdled 
the  stem  just  below  the  surface  of  the  soil  and  formed  a  collar,  or  constriction. 

' '  Lettuce ' '  on  Lettuce. — 125  seeds.  Seeds  germinated  March  13.  By  April 
1  all  the  young  plants  had  damped  off. 

"Poinsettia"  on  Euphorbia  variegata. — 100  seeds.     Seeds  germinated  March 

23.  By  May  22,  6  percent  of  the  plants  had  damped  off. 

"Salvia"  on  Salvia  splendens.- — 100  seeds.  Seeds  germinated  March  23.  By 
May  8,  6  percent  of  the  seedlings  had  damped  off.  By  May  21,  4  of  the  plants 
were  infected.  Lesions  extending  into  the  woody  tissues  were  present  on  the  stem. 

"Salvia"  on  Salvia  splendens. — 48  cuttings.  These  cuttings  rotted  off  very 
rapidly.  Wherever  the  leaves  touched  the  soil,  they  were  rotted  also.  By  April 
7,  41  cuttings  were  diseased  and  7  were  rooted  and  healthy. 

"Sugar  Cane"  on  Amaranthus  salicifolius. — 100  seeds.  Seeds  germinated 
March  23.  On  May  21  all  the  plants  were  perfectly  healthy.  No  infection  waa 
present. 

"Thistle"  on  Clover. — 100  seeds.  Seeds  germinated  March  13.  On  May  21 
all  the  plants  were  healthy. 

Additional  Inoculations. — On  April  1  six  flats  of  infected  soil  used  in  the 
inoculation  experiments  with  carnation  cuttings  were  mixed  with  soil  in  larger 
tlats  and  four  hills  of  potatoes  were  planted  in  each.  The  six  flats  represented  the 


358  BULLETIN  No.  189  [June, 

six  strains  " Alternanthera  B.A.F.,"  "Carnation  R.F.,"  "Cauliflower,"  "Let- 
tuce, ' '  "  Cotton, ' '  and  ' '  Dianthus  barbatus. ' '  Only  one  or  two  potato  sprouts 
came  up  from  each  hill  and  these  were  weak  and  spindling.  After  the  tempera- 
ture became  too  high  in  the  greenhouse,  the  flats  were  placed  outside,  so  that  the 
plants  would  develop  further  and  produce  tubers.  The  strains  killed  some  of  the 
young  sprouts  and  dwarfed  the  others,  showing  that  they  were  able  to  attack  the 
potato  plant. 

Here,  as  in  the  preceding  experiments,  the  death  rate  of  the  vari- 
ous plants  was  quite  variable.  These  differences  appear  to  be  due  to 
the  virulence  of  the  fungus,  to  the  susceptibility  of  the  plant,  or  to  a 
combination  of  factors. 

EXPERIMENT  10 :    INOCULATION  OF  VARIOUS  HOSTS  IN  THE  FIELD 
WITH  VARIOUS  STRAINS  OF  RHIZOCTONIA 

All  the  inoculation  experiments  reported  so  far  were  conducted  in 
the  greenhouse.  In  the  summer  of  1914  a  fourth  of  an  acre  of  land  was 
divided  into  three  parts,  separated  by  six-foot  strips  of  ground.  Sec- 
tion 1  was  inoculated  on  May  20  with  twenty  cubic  feet  of  infected  soil 
taken  from  the  inoculated  benches  in  the  greenhouse.  The  soil  was 
spread  upon  the  section,  worked  under,  and  watered  for  several  days. 
Section  2  was  left  as  a  check.  In  Section  3  small  bits  of  pure  cultures 
of  various  strains  of  Rhizoctonia  were  added  with  the  seeds  and  plants. 
The  seeds  were  planted  May  20,  and  the  young  plants  were  put  in 
June  16.  Altho  the  drouth  of  the  summer  interfered  considerably, 
the  results  obtained  were  sufficient  to  show  that  Rhizoctonia  Solani 
was  active  under  field  conditions  as  well  as  in  the  greenhouse. 

No  infection  occurred  in  the  first  two  sections.  In  Section  3  in- 
fection was  quite  marked  in  a  number  of  cases,  especially  on  cotton, 
potato,  and  several  greenhouse  plants.  Where  the  strain  ' '  Cotton  I ' ' 
was  added  to  the  cotton  seeds,  100-percent  infection  occurred.  In  the 
case  of  potato,  to  which  ' '  Carnation  R.F.2 ' '  was  added,  a  marked  dif- 
ference was  noticed,  the  plants  in  this  section  being  dwarfed  and 
spindling,  while  in  the  first  two  sections  they  were  bushy  and  strong. 
The  difference  in  the  yield  was  as  marked  as  the  difference  in  growth 
of  the  plants.  All  the  coleus  plants  infected  with  "Coleus  I"  were 
killed  within  two  weeks  after  being  set  out.  The  same  results  were 
obtained  from  inoculating  salvia  plants  with  the  strain  from  salvia. 

DISCUSSION  OF  INOCULATION  EXPERIMENTS 

In  Table  11  are  brought  together,  in  tabular  form,  the  results  of 
all  the  inoculation  experiments,  with  the  exception  of  No.  4,  which 
was  carried  on  primarily  to  test  the  comparative  virulence  of  isolated 
and  reisolated  strains  of  Rhizoctonia.  The  thing  that  stands  out  at 
first  glance  is  the  great  variation  in  the  mortality  of  the  plants  when 
inoculated  with  strains  from  the  same  host  and  when  inoculated  with 
strains  from  other  sources. 


1016]  PARASITIC  KHIZOCTONIAS  IN  AMERICA  359 

When  carnation  cuttings  were  infected,  the  strains  used,  with  but 
two  exceptions,  whether  from  carnation  or  from  other  hosts,  were 
able  to  cause  more  or  less  loss,  the  mortality  of  the  cuttings  ranging 
in  either  instance  from  0  to  100  percent.  Again,  the  same  strains 
varied  in  virulence  from  one  year  to  another,  in  most  cases  decreas- 
ing in  virulence  with  age.  When  cuttings  other  than  carnation  were 
used,  the  results  were  the  same. 

When  young  rooted  carnation  plants  were  inoculated,  the  percent- 
age of  loss  was  much  less  than  with  cuttings.  Here,  however,  the  car- 
nation strains  seemed  to  be  slightly  more  virulent  than  those  from 
other  sources,  altho  there  was  still  a  great  difference  in  the  strains 
from  carnation  themselves.  Only  one  of  the  strains  from  other  sources 
was  unable  to  attack  young  rooted  carnation  plants. 

On  old  carnation  plants  in  the  greenhouse  which  were  inoculated 
by  contact,  even  the  carnation  strains  did  not  cause  a  high  percentage 
of  infection.  However,  when  plants  growing  under  these  same  condi- 
tions were  slightly  wounded  and  then  inoculated,  the  percentage  of 
loss  was  very  high  in  nearly  all  the  strains  studied.  When  conditions 
(temperature  and  moisture)  were  favorable  to  the  fungus,  most  of  the 
strains  studied  were  able  to  infect  carnation  plants  as  readily  as  the 
carnation  strains  themselves. 

In  the  majority  of  cases  all  strains  were  able  to  cause  damping-off 
of  various  seedlings.  There  was  a  great  difference  in  the  virulence  of 
strains  when  inoculated  on  the  same  host  from  which  they  had  been 
isolated  and  when  inoculated  on  other  hosts.  Only  occasionally  was 
there  any  indication  of  marked  specialization,  and  in  no  case  was  such 
indication  corroborated  in  succeeding  experiments. 

In  older  plants,  a  marked  difference  in  susceptibility  was  found  in 
the  different  species.  As  a  rule,  the  root  crops  were  highly  susceptible 
to  attacks  of  Rhizoctonia.  Among  these,  beet  appeared  to  be  the  most 
susceptible.  Tomato  and  eggplant  showed  a  very  marked  resistance 
to  Rhizoctonia,  and  this  was  true  to  some  extent  of  the  potato  also, 
altho  under  certain  conditions  it  was  quite  susceptible.  This  varia- 
bility of  resistance  held  true  for  most  of  the  vegetable  and  field  crops 
other  than  root  crops.  Under  ordinary  conditions,  the  majority  of 
floricultural  plants  were  not  subject  to  attacks  of  Rhizoctonia,  altho 
the  mycelium  of  this  fungus  was  known  to  be  present  in  the  soil  or 
even  on  the  plant  itself. 

From  the  fact  that  all  the  strains  studied  showed  the  ability  to 
attack  the  same  species  of  plant  and  produce  the  same  characteristic 
symptoms,  it  seems  clear  that  they  can  be  included  under  one  form, 
A'.  Solani.  These  experiments  show  further  that  the  virulence  of 
R.  Solani  is  very  variable,  as  is  also  the  degree  of  resistance  of  the  vari- 
ous host  plants,  both  depending  on  a  number  of  varying  factors. 


360 


BULLETIN  No.  189 


[June, 


TABLE  11. — SUMMARY  OF  INOCULATION  EXPERIMENTS 


Strain 

Original 
date  of 
isolation 

Date  of 
inoculation 
experiment 

Host 

Condition 

Per- 
centage 
of  loss* 

Alfalfa  

1910 

1913 

Alfalfa 

Seedlings 

95 

Alternanthera   R.A.C. 
Alteruanthera    R.A.F. 

Amaranthus     

1912 
1912 

1913 

1913 
1913 
1913 
1913 
1913 
1914 
1913 
1914 
1913 
1914 
1913 
1914 
1913 
1914 
1913 
1913 

1914 
1914 

Cabbage 
Carnation 
Clover 
Corn 
Tomato 
Alternanthera 

Carnation 

t  > 

)> 

Alternanthera 

Carnation 

>  > 

i  > 
» 
)  t 
» 

Geranium 
A  maranthus 

Plants 
Cuttings 

Seedlings 
>  t 

Plants 

Cuttings 
>  > 

» 

Young  plants 

Cuttings 
a 
» 

Young  plants 
»        » 

Old  plants 

>  >       >  > 

(wounded) 
Cuttings 

20 
38 
15 
0 
0 
100 
92 
96 
20 
100 
90 
100 
66 
40 
0 

50 

87 

Aster     

1913 

1914 
1914 
1914 

salicifolius 
Carnation 

7  ) 

Aster 

Seedlings 
Cuttings 
Young  plants 
Seedlings 

100 
100 
16 
29 

Bean    

1914 
1914 

Carnation 
Bean 

Cuttings 
Seedlings 

23 

5 

Beet  

1913 

1913 
1914 
1914 

Carnation 
t  > 

Beet 

Cuttings 

j  > 

Seedlings 

65 
100 

^0 

Begonia  

1911 

1914 
1914 
1913 
1913 

Carnation 

Cuttings 
Young  plants 
Old  plants 
Cuttings 

100 
33 
25 

ion 

Carnation  E.K  

1911 

1913 
1913 

Young  plants 
Cuttings 

6 

90 

Carnation  R.O  

1911 

1913 
1913 
1913 

1913 

Young  plants 

Old  plants 
»       » 

(wounded) 
Cuttings 

85 
0 

100 

o 

Carnation  K.H. 

1911 

1913 
1913 

1913 

Old  plants 

>  i       » 

(wounded) 
Cuttings 

0 

100 

80 

Carnation   R.S  

1911 

1914 
1914 
1913 
1913 

1913 

>  ) 

Young  plants 

Old  plants 
»        » 

(wounded) 
Cuttings 

100 
50 
0 

100 
82 

1913 
1913 
1913 

Young  plants 

Old 

»           » 

(wounded) 

93 

50 

100 

•In  Experiments  1  and  la  the  loss  from  plants  wilted  is  not  included  in  the 
percentage  of  loss. 


1'JIG] 


PARASITIC  RHIZOCTONIAS  IN  AMERICA 


361 


TABLE  11. — Continued 


Strain 

Original 
date  of 
isolation 

Date  of 
inoculation 
experiment 

Host 

Condition 

Per- 
centage 
of  loss" 

Carnation  R.2    

1912 

1913 

UaTnation 

buttings 

100 

1913 

)  } 

Young  planb 

54 

1913 

>  > 

Old  plants 

50 

1913 

i  i 

11       11 

(wounded) 

100 

Carnation  R.F  

1912 

1913 

Beet 

Seedlings 

98 

1914 

)  > 

i  > 

40 

1913 

Cabbage 

» 

40 

1913 

Carnation 

Cuttings 

100 

1914 

j  > 

94 

1913 

Young  plants 

85 

1913 

j  j        j  > 

100 

1914 

1  1       11 

50 

1913 

Old  plants 

0 

1913 

11       11 

(wounded) 

100 

1913 

Eggplant 

Seedlings 

0 

1913 

Lettuce 

1  1 

60 

1913 

,•  > 

Plants 

50 

1913 

Radish 

Seedlings 

50 

Carnation  R.M.2   

'1912 

1913 

Carnation 

Cuttings 

96 

1914 

;  i 

)  i 

43 

1913 

1  i 

Young  plants 

85 

1913 

'  ' 

Old  plants 

0 

1913 

1  i 

11       11 

(wounded) 

50 

1914 

Carrot 

Seedlings 

10 

Carnation  E  107  

1912 

1913 

Alfalfa 

11 

70 

1913 

Beet 

Plants 

100 

1914 

Cabbage 

Seedlings 

75 

1913 

Carnation 

Cuttings 

92 

1914 

i  i 

11 

91 

1913 

11 

Young  plants 

73 

1913 

i  i 

Old  plants 

0 

1913 

i  i 

11        11 

(wounded) 

100 

1913 

>  > 

Old  plants 

100 

1913 

Clover 

Seedlings 

5 

1913 

Corn 

11 

0 

Carnation  R.F.2  

1913 

1914 

Bean 

11 

3 

1914 

Carnation 

Cuttings 

100 

1914 

.  i  i 

Yroung  plants- 

66 

Carnation  R.121-5.  .  . 

1912 

1913 

Cabbage 

Plants 

70 

1913 

Tomato 

11 

20 

Carnation   (Sections 

157  and 

173)    

1914 

Bean 

11 

98 

Carnation   (Section 

158) 

1914 

Beet 

1  1 

95 

(          163) 

1914 

Cabbage 

1  1 

90 

'(          158) 

1914 

Carrot 

11 

10 

(          153) 

1914 

Corn 

Seedlings 

0 

(          170) 

1914 

Eggplant 

Plants 

0 

(          153) 

1914 

Lettuce 

1  1 

16 

"See  footnote,  page  360. 


362 


BULLETIN  No.  189 


f  June, 


TABLE  11. — Continued 


Strain 

Original 
date  of 
isolation 

Date  of 
inoculation 
experiment 

Host. 

Condition 

Per- 
centage 
of  loss" 

1913 

Beet 

Plants 

0 

Cauliflower     

1912 

1913 
1914 
1913 
1913 
1913 

1914 
1913 
1913 
1913 

Carnation 

>  j 

>  > 
>  t 

>  j 

Carrot 
Radish 
Turnip 
Cabbage 

Cuttings 
i  } 

Young  plants 

Old  plants 
»        » 

(wounded) 
Seedlings 

» 

)> 

66 
30 
13 
0 

0 
5 
98 
50 
98 

Chenopodiuni      

1913 

1914 
1913 
1913 
1914 
1913 
1914 
1913 
1913 
1913 
1914 

,,    & 
>  t 

Carnation 
» 
» 
» 
>  t 

Lettuce 
Tomato 
Alfalfa 

» 

Plants 

Cuttings 
» 

Young  plants 

»        j  > 

Old  plants 
Seedlings 
Plants 
Seedlings 

97 
90 
100 
100 
40 
26 
75 
3 
0 
60 

1912 

1914 
1913 

Carnation 
Alfalfa 

Cuttings 
Seedlings 

31 

100 

Coleus  I       

1912 

1914 
1913 
1914 
1913 
1913 

Carnation 

Clover 

>  j 

Corn 
Carnation 

Cuttings 

Seedlings 
» 

» 
Cuttings 

75 

99 
10 
0 
100 

Coleus  II   

1913 

1914 
1913 
1914 
1914 
1914 
1914 

j  j 
>  j 
» 

Coleus 
>  > 

Carnation 

» 

Young  plants 
»          » 

Seedlings 

Cuttings 

i  j 

100 
40 
23 
100 
100 
100 

Corn     

1912 

1914 
1914 
1914 
1913 

Chrysanthemum 

Coleus 
)  > 

Alfalfa 

)  > 

Seedlings 
Cuttings 
Seedlings 

100 
70 
100 
g 

Cotton  I  

1911 

1914 
1913 
1913 
1914 
1913 

Carnation 
Clover 

Corn 
>  > 

Cabbage 

Cuttings 
Seedlings 
>  > 

>t 
Plants 

51 
2 
0 
0 
50 

Cotton  II  

1912 

1913 
1914 
1913 
1914 
1914 
1913 
1913 

Carnation 
y  > 

)  > 
)  > 

Cotton 
Tomato 
Carnation 

Cuttings 

>  > 

Young  plants 
»         >  ) 

Seedlings 
Plants 
Cuttings 

100 
62 
87 
56 
100 
0 
100 

Cotton  III  . 

1912 

1914 
1913 
1913 
1913 

1913 
1914 

>  > 

Young  plants 

Old  plants 
»         t> 

(wounded) 
Old  plants 
Cuttings 

91 
46 
0 

50 
100 
70 

"See  footnote,  page  360. 


1916] 


PARASITIC  KIIIZOCTONIAS  IN  AMERICA 


363 


TABLE  11. — Continued 


Strain 

Original 
date  of 
isolation 

Date  of 
inoculation 
experiment 

Host 

Condition 

Per- 
centage 
of  loss* 

Cotton  III  

1912 

1913 

Carnation 

Young  plants 

28 

1914 

Cotton 

Seedlings 

100 

Dianthus  barbatus 

g  M          

1913 

1914 

Carnation 

Cuttings 

98 

1913 

>  } 

Old  pjants 

75 

1914 

Dianthus 

barbatus 

Seedlings 

50 

Uiaiithusbarbatus  N.P. 

1913 

1914 

Carnation 

Cuttings 

100 

1914 

» 

Young  plants 

60 

1914 

Dianthus 

barbatus 

Seedlings 

50 

Diauthus   plumarius.  . 

1913 

1914 

Carnation 

Cuttings 

100 

1913 

>  > 

Old  plants 

100 

1914 

Dianthus 

plumarius 

Seedlings 

80 

Dianthus   sequeri  

1913 

1914 

Carnation 

Cuttings 

100 

1914 

Dianthus 

sequeri 

Seedlings 

75 

Kppnlant  I 

1912 

1913 

Carnation 

Cuttings 

42" 

1914 

>  i 

93 

1913 

Young  plants 

60 

1914 

)  )         » 

20 

1913 

Old  plants 

0 

1913 

>  >       >  > 

(wounded) 

100 

1913 

» 

Old  plants 

75 

1913 

Eggplant 

Seedlings 

3 

1914 

)  i 

>  > 

4 

1913 

Lettuce 

>  > 

75 

1913 

» 

Plants 

20 

Eggplant    II  

1913 

1914 

Carnation 

Cuttings 

83 

1914 

Eggplant 

Seedlings 

100 

Lavatera     

1913 

1914 

Carnation 

Cuttings 

98 

1914 

)  ) 

Young  plants- 

36 

1914 

Lavatera 

trimestris 

Seedlings 

95 

Lettuce                

1913 

Carnation 

Cuttings 

0 

1914 

j  > 

i  } 

34 

1913 

i  y 

Young  plants 

13 

1913 

>  > 

Old  plants 

0 

1913 

)  > 

»       >  > 

(wounded) 

100 

1913 

Eggplant 

Seedlings 

2 

1913 

Lettuce 

» 

90 

1914 

» 

100 

1913 

Plants 

0 

Poinsettia     

1912 

1913 

Carnation 

Cuttings 

75 

1914 

>  > 

52 

1913 

Old  plants 

0 

1913 

»       >  •> 

(wounded) 

100 

1914 

Euphorbia 

variegata 

Seedlings 

6 

Potato  E.P.C  

1912 

1913 

Beet 

» 

50 

1913 

>  > 

Plants 

0 

1913 

Carnation 

Cuttings 

90 

1913 

ft 

Young  plants 

0 

"See  footnote,  page  360. 


364 


BULLETIN  Xo.  189 


TABLE  11. — Concluded 


Strain 

Original 
date  of 
isolation 

Date  of 
inoculation 
experiment 

Host 

Condition 

Per- 
centage 
of  loss* 

Potato  R.P.C  

1912 
1912 

1912 

1913 
1912 

1913 
1913 
1913 
1913 
1913 

1913 
1913 
1913 
1913 

1913 
1913 
1913 

1913 
1913 
1913 
1913 
1913 
1914 
1913 
1914 

1914 
1914 
1914 
1914 

1913 
1914 
1913 
1913 
1914 
1913 
1913 
1913 

1914 
1913 
1913 
1914 

Radish 

Carnation 
j> 

>  ; 
j  > 

5  5 
55 

;  > 

>  > 
5  ; 

5  > 

;  5 

Beet 
Radish 
Turnip 

Carnation 

5  5 

» 

Salvia 

splendens 

>  > 

Carnation 

i  5 

Amaranthus 
salicifolius 

Carnation 

5 

5 

5 

! 

> 
5  ' 

Clover 
Eggplant 

Lettuce 
» 

Seedlings 
Cuttings 
Young  plants 
Old  plants 

>  5              55 

(wounded) 
Cuttings 
Young  plants 
Old  plants 

55              55 

(wounded) 
Cuttings 
Old  plants 

55             55 

(wounded) 
Old  plants 
Plants 

Seedlings 

>  } 

Cuttings 
.    » 

Young  plants 

Seedlings 
Cuttings 

7  ) 

Young  plants 

Seedlings 
Cuttings 

5  5 

Young  plants 
Cuttings 

55 

Young  plants 
Old  plants 

55             )  5 

(wounded" 
Seedlings 

}  5 
» 

Plants 

.15 
65 
50 
0 

100 
58 
43 
0 

50 
60 
0 

100 
75 
0 
1 
99 
2 
47 
33 

10 
85 
100 
20 

0 
90 
24 
13 
33 
47 

1 

100 
0 
5 
60 
0 

Potato  R.P.I  

Potato   R.P.O  

Potato  R   Sol  

Radish    

Salvia    

Sedum     

Sugar   cane    

Thistle    

"See  footnote,  page  360. 


GROAVTII  ON  MEDIA 

In  the  course  of  these  studies  thirty-eight  strains  of  Rhizoctonia 
were  grown  on  five  of  the  more  common  vegetable-extract  agars  and  a 
solid  synthetic  medium.  The  composition  of  these  media  may  be  found 
in  the  appendix,  together  with  a  complete  description  of  the  growth 
of  the  various  strains  on  them. 


1916]  PARASITIC  RHIZOCTONIAS  IN  AMERICA  365 

As  a  rule  the  fungus  isolated  from  carnation  plants,  when  grown 
on  green-bean  agar,  produced  a  rapid-growing  mycelium,  which  was 
practically  all  aerial,  loose,  and  tufted.  The  most  characteristic  fea- 
ture was  the  production  of  concentric  zones,  tho  this  was  not  invaria- 
ble. Of  the  many  hundred  cultures  made  during  the  past  three  years 
from  diseased  carnation  plants  on  green-bean  agar,  90  percent  have 
shown  this  zonation.  This  characteristic  was  influenced  by  neither 
light  nor  temperature.  A  typical  growth  on  this  medium  is  shown  in 
Fig.  20,  "Carnation  R.H."  A  few  of  the  carnation  strains  grown 
on  the  same  medium  and  showing  the  same  type  of  mycelium  produced 
very  indistinct  zonation  or  none,  as  shown  in  Fig.  20,  "Carnation 
R.F."  Zonation  persisted  to  some  extent  when  the  carnation  strains 
were  grown  on  other  media  than  green-bean  agar,  but  it  was  not  so 
characteristic. 

The  two  strains  from  potato  did  not  grow  so  rapidly  nor  quite 
so  luxuriantly  on  green-bean  agar  as  did  the  carnation  strains,  but 
they  produced  the  same  even,  tufted,  zonate  growth.  Here  the  zones 
were  closer  together.  (See  Fig.  20,  "Potato  R.  Sol.") 

The  growth  of  the  strain  from  corn  on  green-bean  agar  was  similar 
to  that  of  "Potato  R.  Sol." 

The  growth  on  green-bean  agar  of  the  strains  from  eggplant,  let- 
tuce, Chenopodium,  and  thistle  was  different  from  any  of  the  other 
forms  in  that  the  mycelium  grew  along  the  surface,  running  out  ra- 
dially in  strands,  which  became  larger  and  more  tufted  at  the  edge. 
(See  Fig.  21,  "Eggplant  I.") 

The  strains  isolated  from  alternanthera,  coleus,  salvia,  and  poin- 
settia,  when  grown  on  green-bean  agar,  showed  the  same  even,  fluffy 
to  tufted  growth.  This  was  also  characteristic  of  the  strains  from 
cauliflower,  cotton,  and  sugar  cane.  Zonation  in  these  strains  was 
varied.  (See  Fig.  21.) 

The  strain  from  onion  when  grown  on  this  agar  differed  radi- 
cally from  the  others.  The  mycelium  was  bright  colored,  finer,  and 
almost  all  submerged.  (See  Fig.  20.) 

The  other  strains  studied  on  green-bean  agar  cannot  be  put  in 
definite  groups,  as  they  shade  into  one  another.  However,  the  growth 
of  the  mycelium  was  somewhat  similar  in  each  case;  practically  the 
only  difference  noted  was  in  the  extent  of  the  zonation. 

On  corn-meal  agar  the  growth  of  the  strains  was  similar  to  a  large 
extent ;  the  only  great  difference  noted  was  in  rapidity  of  growth. 
Zonation  was  very  rare  on  this  medium. 

The  growth  of  the  strains  on  oat  agar  was  somewhat  variable; 
zonation  was  sometimes  present  and  sometimes  absent. 

The  most  characteristic  feature  of  the  growth  of  the  majority  of 
the  strains  on  potato  agar  was  the  turning  brown  of  both  the  myce- 
lium and  the  medium.  This  same  characteristic,  but  to  a  less  degree, 


366 


BULLETIN  No.  189 


[June, 


FIG.  20. — CULTURES  OF  RHIZOCTONIA  STRAINS  SHOWING  DEVELOPMENT  OF  MYCE- 
LIUM ON  GREEN-BEAN  AGAR  (CULTURE  48  HOURS  OLD).  Top  Row:  (1)  CAR- 
NATION R.H.;  (2)  CARNATION  R.F.  MIDDLE  Row:  (1)  POTATO  R.  HOL.;  (2) 
CARROT.  BOTTOM  Row:  (1)  CAULIFLOWER;  (2)  ONION 


1016] 


PARASITIC  RHizoctONlAS  IN  AMERICA 


367 


FIG.  21.— CULTURES  OF  BHIZOCTONIA  STRAINS  SHOWING  DEVELOPMENT  OF  MYCE- 
LIUM ON  GREEN -BE  AN  AGAR  (CULTURE  48  HOURS  OLD).  TOP  Bow:  (1)  ALTER - 
NANTHERA'B.A.F.;  (2)  ALTERNANTHERA  B.A.C.  MIDDLE  Bow:  (1)  POIN- 
SETTIA;  (2)  COLEUS  I.  BOTTOM  Bow:  (].)-  EGGPLANT  I;  (2)  LETTUCE 


368 


BULLETIN  No.  189 


f  June, 


FIG.  22. — CULTURES  OF  EHIZOCTONIA  STRAINS  SHOWING  DEVELOPMENT  OF  SCLERO- 
TIA:   (1)  ALTERNANTHERA  R.A.C.;   (2)  SALVIA;   (3)  POINSETTIA;   (4)  ALTER- 

NANTHERA    E.A.F. ;     (5)    COLEUS ;     (6)     EGGPLANT    II;     (7)     EGGPLANT    I;     (8) 

LETTUCE;  (9)  CHENOPODIUM;  (10)  THISTLE;  (11)  CARNATION  E.F.2;  (12) 
CARNATION  E.S.;  (13)  CARNATION  E.2;  (14)  CARNATION  E.H.;  (15)  CARNA- 
TION E.G.;  (16)  ASTER;  (17)  COTTON  I;  (18)  BEET;  (19).  CARROT;  (20) 
BEAN 


1916] 


PARASITIC  RHIZOCTONIAS  IN  AMERICA 


369 


FIG.  23. — CULTURES  OF  RHIZOCTONIA  STRAINS  SHOWING  DEVELOPMENT  OF  SCLEHO- 
TIA:  (1)  AMARANTHUS;  (2)  PANSY;  (3)  LAVATERA;  (4)  SWEET  ALYSSUM; 
(5)  LOBELIA;  (6)  ALFALFA; (7)  CLOVER;  (8)  CORN;  (9)  CAULIFLOWER;  (10) 
SUGAR  CANE;  (11)  BUCKWHEAT;  (12)  RED  CLOVER;  (13)  SEDUM;  (14) 
GYPSOPHILA;  (15)  ONION;  (16)  DIANTHUS  BARBATUS  S.M. :  (17)  DIANTHUS 
PLUMARIUS;  (18)  DIANTHUS  SEQUERI;  (19)  DIANTHUS  BARBATUS  N.P.;  (20) 
ASTER  (CARNATION  STRAIN) 


370  BULLETIN  No.  189  [June, 

was  found  with  the  growth  on  potato-glucose  agar.  On  both  these 
media  zonation  was  usually  lacking  or  indistinct. 

On  Agar  XII  most  of  the  strains  grew  rather  poorly  and  produced 
a  white,  flaky  growth,  with  varying  zonation. 

Early  in  the  study  of  the  characters  of  the  strains  on  culture 
media,  it  was  noticed  that  as  there  were  characteristic  differences  in 
growth,  so  also  were  there  differences  in  the  production  of  sclerotia. 

The  strains  "Eggplant  I,"  "Lettuce,"  "  Chenopodium, "  and 
"Thistle"  on  green-bean  agar  all  formed  sclerotia  in  a  characteristic 
manner.  The  sclerotia  were  white  at  first  and  flat,  later  turning  black, 
and  as  the  culture  became  older,  curling  up  and  becoming  crust-like. 
All  four  of  the  forms  mentioned  above  showed  these  same  character- 
istics, altho  they  were  originally  obtained  from  widely  separated  locali- 
ties. (See  Fig.  22.)  The  strain  from  onion  produced  sclerotia  which 
were  entirely  different  from  those  of  other  strains  in  that  they  were 
small  (.5  to  1  millimeter  in  diamater),  perfectly  round,  bright  colored, 
and  developed  submerged  in  the  medium.  (See  Fig.  23.)  The  strains 
"Buckwheat,"  "Carnation  R.O.,"  " Gypsophila, "  and  "Sedum" 
rarely  produced  sclerotia  in  culture.  Repeated  observations  showed 
that  this  loss  of  power  to  produce  sclerotia  was  the  first  sign  of  the  de- 
generation and  loss  of  virulence  of  the  strain. 

All  the  other  strains  studied  produced  sclerotia  which  were  at  first 
white,  later  becoming  brown.  Altho  the  sclerotia  from  the  strain  from 
potato  are  similar  to  those  from  carnation  when  grown  on  culture 
media,  on  the  potato  tuber  they  are  entirely  different.  For  the  most 
part  the  Rhizoctonia  sclerotia  on  potato  tubers  which  the  writer  has 
examined  are  flat  and  hard,  have  a  black  luster,  and  are  in  many  re- 
spects like  the  sclerotia  produced  in  culture  media  by  the  strains  from 
eggplant,  lettuce,  etc. 

The  only  conclusion  that  can  be  drawn  from  this  study  of  the 
growth  of  Rhizoctonia  Solani  on  media  is  that  the  strains  are  very 
variable,  those  from  the  same  host  often  producing  a  different  growth, 
even;  on  the  same  media,  and-  that  the  differences  in  various  cultural 
characters  which  are  shown  by  strains  from  different  hosts  are  no 
greater  than  differences  which  may  be  manifested  by  two  different 
strains  isolated  from  the  same  host  or  by  the  same  strain  at  different 
ages. 

MEASUREMENT  OF  MYCELIAL  CELLS 

It  was  rather  difficult  to  choose  a  standard  in  the  measurement  of 
the  mycelial  cells,  because  the  cells  varied  in  size  at  different  ages  and 
on  different  media.  Finally  the  following  standard  was  chosen: 
Hyphae  from  the  outer  edge  of  a  twenty-four  hour  old  culture  on 
green-bean  agar  were  selected  at  random.  The  length  and  width  of 
a  cell  from  which  the  branch  arose  nearest  the  tip  of  the  hypha,  and 


1916] 


PARASITIC  RHIZOCTONIAS  IN  AMERICA 


371 


the  distance  on  the  inner  side  from  the  parent  hypha  to  the  first  sep- 
tum of  the  branch,  were  measured.  Ten  cells  of  each  strain  were 
measured,  and  the  averages  of  these  measurements  used  for  compari- 
son. 

As  shown  in  Table  12,  the  measurements  varied  considerably,  and 
this  was  true  even  with  strains  from  the  same  host.  In  the  three  car- 
nation strains  measured,  the  length  of  the  mycelial  cells  varied  from 
TOfji.  to  181. 1^,  a  difference  of  111.7/x.  However,  the  average  of  ten 
measurements  brings  the  difference  down  to  some  extent.  A  still  more 
striking  difference  was  noted  in  the  strains  from  Dianthus,  where 
the  smallest  reading  was  50//,  and  the  largest  215/*,  a  difference  of  165/A. 
Similar  differences  were  also  found  in  comparing  the  two  other  meas- 
urements. 

In  all  cases,  altho  the  table  does  not  bring  out  this  point,  different 
measurements  of  the  cells  of  the  various  strains  overlapped.  For  ex- 

TABLE  12. — MEASUREMENTS  OF  MYCEIJAL  CELLS  OP  EHIZOCTONIA 


Strain 

Length 
of  cell 

Width 
of  cell 

Distance   from 
cell  to  septum 
of  branch 

Alfalfa              

u 

152.04 

H 

5.76 

V. 

10.08 

Alternanthera    R.A.C  

113.40 

3.92 

6.72 

"              B  A  F                     

124.60 

4.94 

9.32 

107.80 

4.83 

7.98 

180.04 

6.57 

13.08 

Beet                      

77.92 

4.34 

6.52 

Carnation  R  H  

116.09 

4.59 

10.83 

'  '          R.M.2      

141.40 

5.60 

10.49 

'  >          E.F.2     

128.15 

5.19 

10.92 

Carrot    

116.64 

4.42 

9.60 

Cauliflower          

119.64 

4.20 

9.60 

Chenopodium    

175.56 

5.43 

11.20 

Clover    

88.20 

5.32 

8.53 

Coleus  I        

117.60 

5.04 

10.21 

Coleus  II    

133.28 

4.97 

10.22 

Corn     

101  64 

4.39 

9.24 

Cotton  I  

65.24 

5.50 

10.18 

Dianthus  barbatus  S.M  
N.P  

113.12 
161.00 

5.58 
5.27 

9.44 
10.58 

sequeri    

131.60 

6.29 

6.44 

plumarius  .  . 

166  95 

5.65 

13.44 

Eggplant  I  

13234 

4.20 

11.65 

"         II    

148  88 

5.60 

9.57 

Gypsophila   repens    

122  08 

3.55 

8.03 

Lavatera     

91  84 

5  89 

9  18 

Lettuce    

119  92 

439 

10  54 

Poinsettia     

126  20 

3.44 

7.92 

Salvia    

111  16 

5  01 

9  93 

Sedum  

90  80 

4  48 

7  00 

Sugar  cane  

113  12 

409 

657 

Sweet  pea  

13048 

5  04 

854 

Thistle     

138.08 

4.62 

11.48 

372  BULLETIN  No.  189  [June, 

ample,  while  the  average  length  of  a  cell  from  "Cotton  I"  was  only 
65/t,  the  largest  reading  was  127. .V,  which  was  higher  than  the  small- 
est measurement  of  a  cell  of  the  strain  "  Chenopodium, "  whose  aver- 
age reading  was  110/u  higher  than  that  of  "Cotton  I."  If  measure- 
ments are  made  of  hyphae  forty-eight  hours  old,  the  differences  are  still 
more  striking,  even  in  the  same  strain. 

Hence,  on  the  measurement  of  mycelial  cells  of  Rhizoctonia  Solani, 
as  on  the  study  of  the  growth  on  media,  no  conclusions  can  be  based  in 
regard  to  distinguishing  the  strains  of  this  difficult  species. 

SOIL  SURVEY  OF  RHIZOCTONIA 

As  shown  in  Table  1,  Rhizoctonia  Solani  has  been  observed  in  al- 
most every  state  in  the  Union,  and  causes  injury  to  a  large  number  of 
plants  under  various  conditions  and  in  widely  different  types  of  soils. 
To  determine  to  how  great  an  extent  Rhizoctonia  is  actually  present 
in  the  soil,  several  surveys  were  made  at  the  University  of  Illinois  in 
fields  containing  a  variety  of  plants. 

Survey  of  ihe  Perennial  Garden,  Horticultural  Grounds,  April  28 
to  May  1,  1914. — During  the  summer  and  fall  of  1913,  Rhizoctonia 
was  isolated  from  a  number  of  perennial  plants  in  the  garden.  To 
determine  whether  the  fungus  lived  on  the  dead  parts  of  the  plants 
or  in  the  soil  or  both  during  the  winter  season,  a  survey  was  made  the 
following  spring. 

Since  it  is  somewhat  difficult  to  isolate  Rhizoctonia  directly  from 
the  soil  by  means  of  soil  cultures,  the  following  method  was  devised 
to  determine  its  presence  in  the  soil:  Small  patches  of  ground  were 
selected  over  the  field  about  twenty  feet  apart,  so  that  the  results  might 
give  a  fair  idea  of  the  distribution  of  the  fungus.  Each  space  was 
cleared  except  for  a  small  living  plant,  and  the  soil  thoroly  watered. 
Three  sheets  of  moistened  filter  paper  were  then  placed  on  the 
ground  over  the  plant.  To  prevent  evaporation,  a  small  flat  with  a 
layer  of  wet  moss  attached  to  the  bottom  was  placed  over  the  paper. 
The  flats  had  previously  been  sterilized  in  formalin  (1-100)  and  the 
moss  sterilized  in  the  autoclave.  Thru  several  small  holes  in  the  bot- 
tom of  the  flat,  water  was  added  to  the  moss  from  day  to  day  to  keep 
it  moist.  At  the  end  of  the  fifth  day  the  plant  parts  were  removed 
to  the  laboratory. 

The  presence  of  the  fungus  was  determined  by  means  of  pure  cul- 
tures and  by  microscopic  observation.  Where  the  identification  de- 
pended solely  on  microscopic  observations,  the  material  was  left  in  a 
covered  dish  for  several  days  until  the  strands  of  the  fungus  became 
older,  when  they  could  be  distinguished  more  readily  by  their  color. 

In  thirteen  cases  out  of  sixteen  Rhizoctonia  was  found  present  on 
the  dead  or  living  pieces  of  plants  placed  in  contact  with  the  soil; 


PARASITIC  RHIZOCTONIAS  IN  AMERICA 


373 


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374  BULLETIN  No.  189 

hence  we  may  conclude  that  this  fungus  was  very  abundant  both  in  the 
soil  and  on  the  plant  parts  in  contact  with  the  soil. 

Survey  of  Plot  Used  for  Field  Inoculation  Experiments,  May  6 
to  May  11,  1914. — This  plot,  formerly  used  by  the  Agronomy  Depart- 
ment, had  been  under  cultivation  for  a  number  of  years.  The  pre- 
vious season  the  field  had  been  in  potatoes  and  corn.  The  old  potato 
stalks  were  left  scattered  over  the  field  during  the  winter. 

A  survey  of  the  plot  was  made  before  plowing,  following  the  same 
method  as  was  used  as  in  the  preceding  experiment.  Sixteen  flats 
were  set  out  twenty-five  feet  apart.  After  five  days  an  examination  for 
the  presence  of  Rhizoctonia  was  made.  By  microscopic  examination 
and  pure  cultures,  Rhizoctonia  was  detected  in  ten  trials  out  of  sixteen 
on  this  plot. 

Survey  of  Agronomy  Plots  on  North  Farm,  September  26  to  Octo- 
ber 2,  1914. — Here  a  more  extensive  survey  was  conducted.  The 
agronomy  plots  on  the  North  Farm  were  chosen  for  this  purpose  be- 
cause of  the  fact  that  they  had  been  under  continuous  cultivation 
since  1895,  and  showed  the  effects  of  different  methods  of  soil  treat- 
ment, various  systems  of  crop  rotation,  and  the  application  of  differ- 
ent kinds  of  food.  (For  treatments  and  rotations  used,  see  Fig.  24.) 
These  plots  are  also  typical  of  the  prairie  soil,  which  represents  the 
most  extensive  and  important  type  of  soil  in  Illinois. 

The  procedure  followed  in  this  survey  was  modified  as  follows: 
In  stead  of  a  flat,  a  seven-inch  flower  pot,  which  could  be  easily  steri- 
lized and  dried,  was  employed.  Small  cheesecloth  bags  were  filled  with 
sphagnum  moss ;  these  were  sterilized  in  the  autoclave.  When  ready 
for  use,  the  bags  were  moistened  and  placed  in  the  bottom  of  the  pots 
and  secured  in  such  a  way  that  they  remained  in  position  when  the 
pots  were  inverted.  A  small  patch  of  soil,  one  in  each  plat,  was  lev- 
eled off,  only  a  small  living  plant  or  some  plant  debris  being  left. 
Several  thicknesses  of  moistened  filter  paper  were  then  laid  over  the 
spot,  and  a  flower  pot  was  placed  over  the  whole.  The  pot  was  pushed 
into  the  ground  about  three  inches  and  the  soil  heaped  up  around  it 
on  the  outside.  The  pots  were  left  in  this  condition  about  one  week, 
during  which  time  the  moss  was  moistened  at  intervals.  Conditions 
were  very  favorable  to  the  growth  of  Rhizoctonia  if  it  was  present 
in  the  soil.  When  the  pots  were  lifted,  the  plant  parts  or  debris  with 
some  of  the  soil  were  wrapped  in  the  filter  paper  and  placed  under 
bell  jars.  The  contents  of  the  papers  were  then  examined  for  the 
presence  of  Rhizoctonia. 

These  plots  showing  the  effects  of  diverse  treatments  yielded  R. 
Solani  in  sixty-four  trials  out  of  seventy.  The  six  negative  results 
were  scattered  over  the  field,  so  that  no  correlation  between  the  treat- 
ment of  the  plot  and  the  presence  of  Rhizoctonia  can  be  said  to  exist, 


1916]  PARASITIC  BHIZOCTONIAS  IN  AMERICA  375 

The  results  of  these  experiments  admit  of  no  question  as  to  the 
presence  of  the  fungus  Khizoctonia  Solani  in  the  soil  in  the  vicinity 
of  Urbana. 

PARASITISM  OF  RHIZOCTONIA  SOLANI  KUHN 

That  R.  Solani  is  an  active  parasite  under  certain  conditions  would 
never  be  questioned  by  anyone  who  had  seen  a  severe  attack  of  car- 
nation stem  rot  in  the  field  or  greenhouse.  In  the  cutting  bench 
this  fungus  causes  damping-off  of  cuttings  in  an  incredibly  short  time, 
while  seedlings  damp  oft'  almost  as  fast.  At  times  Rhizoctonia  causes 
considerable  loss  in  potato  fields.  In  fact,  it  may  become  epidemic 
and  cause  serious  injury  to  most  of  the  field,  vegetable,  and  floricul- 
tural  crops. 

The  epidemics  are  apparently  due  to  a  combination  of  factors, 
such  as  the  presence  of  a  virulent  strain  of  the  fungus,  a  susceptible 
variety  of  plant,  and  optimum  conditions  of  temperature  and  moisture 
for  infection  and  development.  Under  ordinary  conditions  most  of 
the  strains  appear  to  be  weak  parasites. 

The  apparently  universal  presence  of  Rhizoctonia  in  the  soil, 
where  it  can  live  indefinitely  on  dead  organic  matter  under  ordinary 
conditions,  makes  it  a  dangerous  fungus.  The  fact  that  it  shows  no 
marked  specialization  and  can  attack  a  large  variety  of  weeds  assists 
in  harboring  the  fungus  and  in  keeping  up  its  virulence.  The  sclero- 
tia  and  mycelium  can  live  under  adverse  conditions  for  several  years. 
Transfers  from  soil  cultures  started  in  December,  1911,  kept  in  the 
laboratory,  and  allowed  to  dry  out,  yielded  pure  cultures  as  late  as 
July,  1914.  Soil  cultures  left  in  the  field  during  the  entire  winter 
yielded  the  fungus  in  the  spring. 

In  all  but  one  of  the  experiments  inoculation  was  brought  about 
without  wounding  the  plants  in  any  way,  in  many  cases  the  fungus 
being  simply  mixed  with  the  soil  in  which  the  plants  were  growing. 
The  results  furnish  convincing  proof  of  the  parasitism  of  the  fungus. 
The  conditions  under  which  all  strains  manifested  their  greatest  para- 
sitism were  primarily  a  high  temperature  (above  88°  F.)  and  a  soil 
moisture  content  either  too  low  or  too  high  for  the  best  development  of 
the  plant.  When  carnation  plants  growing  in  soil  inoculated  with 
Rhizoctonia  were  given  a  heavy  watering  and  the  soil  was  then  allowed 
to  dry  out,  they  were  killed  more  rapidly  than  plants  growing  under 
the  same  conditions  but  in  continually  over-watered  soil.  Plants 
watered  normally  died  off  slowly  and  the  percentage  of  loss  was  very 
much  less. 

Repeated  observations  in  greenhouse  and  field  have  shown  that  a 
certain  amount  of  the  mycelium  must  be  present  before  the  fungus  is 
able  to  attack  and  kill  the  plant.  A  small  amount  of  mycelium  has 
always  been  observed  around  a  carnation  plant  in  the  bench  a  week 


376  BULLETIN  No.  189  [June, 

or  more  before  the  plant  showed  any  signs  of  being  diseased.  In  fact, 
a  certain  amount  of  mycelium  is  always  present  in  the  carnation  soil 
in  the  greenhouse,  but  it  is  only  when  the  temperature  is  high  that 
the  fungus  is  able  to  attack  the  plants.  This  explains  why  stem  rot 
of  carnations  is  more  severe  during  the  summer  months  than  in  the 
winter.  (See  Experiment  6,  page  349.)  In  the  field  similar  conditions 
are  necessary  to  result  in  infection  of  a  plant. 

Investigations  to  determine  how  much  vigor  the  mycelium  must 
attain  before  the  fungus  can  attack  a  plant  are  now  in  progress,  as 
is  also  a  histological  and  enzymatic  study. 

SUMMARY 

1.  At  the  present  time  there  are  recognized  in  America  two 
species  of  truly  parasitic  Rhizoctonias :  The  common  form,  RMzoctonia 
Solani  Kiihn  (Corticium  vagum  B.  &  C.),  widely  distributed  and  oc- 
curring on  a  great  number  of  hosts;  and  R.  Crocorum  (Pers.)  DC., 
with  a  limited  distribution  on  alfalfa  and  potato  tubers.     A  third 
RMzoctonia,  Corticium  ochraleucum  (Noack)  Burt,  is  found  on  the 
leaves  of  pomaceous  fruit  trees,  while  a  fourth  species  isolated  from 
damped-off  onion  seedlings  is  of  questionable  parasitism. 

2.  The  plants  thus  far  listed  as  more  or  less  subject  to  attacks  of 
RMzoctonia  Solani  Kiihn  in  the  United  States  number  about  165 
species.    All  the  more  important  families  of  dicotyledons  are  included 
in  this  list,  as  well  as  a  number  of  monocotyledons,  several  gymno- 
sperms,  and  Equisetum.     Most  of  the  Agricultural  plants,  vegetable 
and  field  crops,  herbaceous  plants,  and  many  weeds  are  susceptible  to 
attacks  of  this  fungus. 

3.  The  symptoms  produced  by  Rhizoctonia  Solani  Kiihn  in  nat- 
ural infection  are  largely  similar  when  appearing  on  the  same  type 
of  host.    The  damping-off  of  seedlings  and  cuttings  of  various  plants 
is  identical,  as  is  the  rotting  of  a  number  of  root  crops.    In  most  her- 
baceous plants  a  stem  rot  is  produced,  the  symptoms  of  which  are  also 
identical  on  the  various  hosts.     On  very  resistant  plants  lesions  only 
are  formed ;  these  are  apparently  the  same  on  the  different  hosts. 

4.  From  these  inoculation  experiments  with  a  large  number  of 
different  types  of  plants,  we  must  conclude  that  all  the  strains  studied, 
which  were  obtained  from  a  wide  range  of  hosts  of  diverse  geographi- 
cal origin,  can  attack  the  same  species  of  plant  and  produce  the  same 
characteristic  symptoms.  No  marked  specialization  was  noted  in  any  of 
the  strains.     Thus  all  the  strains  studied  can  be  included  under  one 
form,  Rhizoctonia  Solani  Kiihn.     The  inoculation  experiments  show 
further  that  the  virulence  of  R.  Solani  is  very  variable,  as  is  also  the 
degree  of  resistance  of  the  various  host  plants,  both  depending  on  a 
number  of  varying  factors. 


1916]  PARASITIC  KHIZOCTONIAS  IN  AMERICA  377 

5.  Studies  of  the  growth  of  Rliizoctonia  Solani  Kiihn  on  media 
show  that  the  strains  are  very  variable,  those  from  the  same  host 
often  producing  a  different  growth  even  on -the  same  media,  and  that 
the  differences  in  various  cultural  characters  which  are  shown  by 
strains  from  unlike  hosts  are  no  greater  than  the  differences  which 
may  be  manifested  by  two  different  strains  isolated  from  the  same  host 
or  by  the  same  strain  at  different  ages. 

6.  Measurements  of  mycelial  cells  of  Rhizoctonia  Solani  Kiihn 
showed  such  large  variations,  not  only  between  strains  from  different 
hosts  but  also  between  different  strains  from  the  same  host,  that  no 
standard  could  be  determined  on   for  distinguishing  the   different 
strains. 

7.  By  means  of  a  local  soil  survey,  it  was  found  that  RJiizoctonia 
Solani  Kiihn  is  abundant  in  cultivated  land,  where  it  may  live  either 
on  dead  organic  matter  in  the  soil  or  on  weeds  and  other  plants. 

8.  A  certain  vigor  of  mycelium  must  be  attained  before  Rliizoc- 
tonia  Solani  Kiihn  is  able  to  attack  a  plant.      A  high  temperature 
(88°  F.),  together  with  either  too  little  or  too  much  moisture,  deter- 
mines to  a  large  degree  the  virulence  of  the  strains.    It  is  only  under 
certain  conditions  that  the  fungus  becomes  a  dangerous  parasite. 


The  writer  gratefully  acknowledges  his  indebtedness  to  Dr.  F.  L. 
Stevens,  Professor  of  Plant  Pathology,  and  to  Dr.  J.  T.  Barrett,  for- 
mer Chief  Assistant  in  Botany,  for  their  kind  assistance  and  encour- 
agement. He  wishes  also  to  thank  Professor  H.  B.  Dorner,  Assistant 
Chief  in  Floriculture ;  Mr.  C.  C.  Rccs,  formerly  Assistant  in  Floricul- 
tural  Pathology;  and  other  members  of  the  Division  of  Floriculture 
for  assistance  rendered  during  the  progress  of  this  work. 


378  BULLETIN  No.  189  [June, 

APPENDIX 

COMPOSITION  OF  MEDIA  USED  IN  EXPERIMENTS 

Corn-Meal  Agar  (Shear*). — To  4  teaspoonfuls  of  corn  meal  add  1  liter  of  dis- 
tilled water.  Keep  in  water  bath  for  one  hour  at  a  temperature  below  60°C. 
Strain  thru  gauze,  and  to  the  filtrate  add  1  percent  agar  flour.  Steam  three-quarters 
of  an  hour.  Filter  thru  paper  tube  and  place  in  autoclave  for  15  minutes  at 
115°  C. 

Green-Bean  Agar. — 300  grams  young  string  beans  cooked  in  500  cc  water 
for  one  hour  and  strained  thru  cloth.  15  grams  agar  (powdered)  melted  in  500  cc. 
water.  Mix  the  two,  add  enough  water  to  make  1000  cc.,  add  6  to  8  grains  egg 
albumen,  and  boil  in  autoclave.  Filter  thru  cotton. 

Oat  Agar  (Clinto^). — 200  grams  oats  ground  fine  thru  a  coffee  mill  and 
soaked  in  500  cc.  water  for  one  hour.  15  grams  agar  melted  in  500  cc.  water  and 
strained  thru  cheesecloth.  Mix  the  two  but  do  not  filter,  since  the  most  nutrient 
part  of  the  medium  would  be  lost. 

Potato  Agar. — 300  grams  peeled  potatoes,  sliced  as  thin  as  possible  and  cooked 
in  500  cc.  water  for  one  hour.  Strain  thru  cloth.  15  grams  agar  (powdered) 
melted  in  500  cc.  water.  Mix  the  two  and  add  enough  water  to  make  1000  cc. 
Add  6  to  8  grams  egg  albumen  (powdered)  and  boil  in  autoclave  for  a  short  time. 
Filter  thru  cotton. 

Potato-Glucose  Agar.— 290  grams  peeled  potatoes,  sliced  as  thin  as  possible 
and  cooked  in  500  cc.  water  for  one  hour.  Strain  thru  cloth  and  add  20  grams  of 
glucose.  15  grams  agar  (powdered)  melted  in  500  cc.  water.  Mix  the  two,  add 
enough  water  to  make  1000  cc.,  add  6  to  8  grams  egg  albumen  (powdered),  and 
boil  in  autoclave  for  short  time.  Filter  thru  cotton. 


Agar  (Cookc) 
Water     

1000.00  cc. 

ims 

Aear 

15.00  grf 

Glucose       

20.00 

Ammonium  nitrate   

1.00 

Potassium  nitrate   

1.00 

Ammonium  sulfate   

1.00 

Magnesium  sulfate   

25 

Dipotassium  phosphate  

25 

Calcium  chlorid".  . 

.01 

GROWTH  ON  MEDIA 

' '  ALFALFA  ' ' 

On  Corn-Meal  Agar. — Growth  poor  and  rather  slow.  Mycelium  white,  fine, 
submerged,  and  scarcely  visible.  No  coloring  of  the  medium.  No  zonation. 

On  Green-Bean  Agar. — Growth  poor  and  slow.  Mycelium  white,  fine,  loose, 
and  becoming  somewhat  tufted.  Zonation.  Like  strain  from  corn. 

On  Potato  Agar. — Growth  rather  slow.  Characterized  by  the  dark  color 
of  the  mycelium  and  the  turning  of  the  medium  to  a  darker  color.  Hyphsu  loose, 
fine,  and  practically  all  submerged.  No  zonation. 

»U.  S.  Dept.  Agr.,   Bur.  Plant  Indus.,   Bui.  252,   15.     1913. 
bConn.  Sta.  Rpt.   (1909-10),  32,  760.    1911. 
cDel.  Sta.  Bui.  91,  12.     1911. 
dOmitted  from  formula  used. 


1916]  PARASITIC  BHIZOCTONIAS  IN  AMERICA  379 

Stewart,1"5  in  reporting  the  damping-off  of  alfalfa  seedlings  in  the  greenhouse 
and  the  crown  rot  of  mature  plants  in  the  field,  states  that  "the  one  causing 
dampiner-off  of  seedlings  in  the  greenhouse  is  different  from  the  one  found  in  the 
field.  When  grown  on  potato  agar  (slightly  acid,  neutral,  or  slightly  alkaline), 
the  former  produces  a  conspicuous  dark  brown  discoloration  of  the  medium,  whereas 
the  latter  discolors  it  only  slightly.  This  character  may  be  useful  in  the  identi- 
fication of  the  damping-off  Rhizoctonia.  Such  discoloration  of  the  medium  is  not 
common  among  the  species  of  Ehizoctonia. "  It  is  interesting  to  note  that  the 
strain  obtained  from  Louisiana  causing  a  damping-off  of  alfalfa  seedlings  and  a 
number  of  other  strains  showed  the  same  discoloration  as  the  one  studied  by 
Stewart. 

On  Agar  XII. — Growth  fair.  Few  loose,  erect  hyphse,  becoming  denser  and 
finally  forming  an  indistinct  zone. 

"  ALTERNANTHERA  B.  A.  C." 

On  Corn-Meal  Agar. — Growth  very  rapid,  but  not  dense.  Mycelium  white, 
loose,  aerial,  and  fine.  No  zonation. 

On  Green-Bean  Agar. — Growth  good.  Mycelium  tufted  and  compact,  not 
turning  darker.  Zonation  somewhat  distinct  at  end  of  third  day.  Three  zones 
present. 

On  Oat  Aoor. — Growth  rapid.  Mycelium  flat,  and  very  compact,  forming  a 
mat  over  the  surface.  Zonation. 

On,  Potato  Agar. — Growth  very  rapid,  with  zone  formation  beginning  im- 
mediately. Mycelium  all  aerial  and  growing  very  compactly.  Plate  was  covered 
at  end  of  forty-eight  Lours  and  showed  two  distinct  zones  and  one  indistinct. 

On  Potato-Glucose  Agar. — Growth  rapid;  plate  covered  in  forty-eight  hours. 
Mycelium  white,  loose,  and  flaky.  Zonation. 

On  Agar  XII. — Growth  good.  Mycelium  white,  fine,  compact,  and  somewhat 
flaky.  Zonation. 

.  ' '  ALTERNANTHERA  E.  A.  F. ' ' 

On  the  various  media  this  strain  produced  the  same  kind  of  growth  in  each 
case  as  the  strain  from  the  cutting  bench,  except  that  it  grew  more  rapidly. 

' '  ASTER  ' ' 

On  Green-Bean  Agar. — Growth  fair.  Mycelium  white,  loose,  regular,  :oid  flat, 
becoming  somewhat  tufted.  Four  zones  formed  at  end  of  the  fourth  day. 

On  Oat  Jf/er.— Growth  fair.  Mycelium  white,  loose,  flat,  and  regular,  be- 
coming fluffy  and  tufted.  Like  strain  ' '  Carnation  E.  F. "  Five  zones  at  end  of 
fourth  day. 

On  Potato-Glucose  Agar. — Growth  slow  and  poor.  Mycelium  mostly  submerged 
and  turning  brown.  No  zonation. 

On  Agar  XII. — Growth  fair.  Mycelium  white,  loose,  flat,  and  regular,  be- 
coming somewhat  tufted.  Zonation. 

"BEAN" 

On  Corn-Meal  Agar. — Growth  very  poor;  scarcely  visible.  Mycelium  white, 
fine,  somewhat  aerial.  No  zonation. 

On  Grcen-'Bean  Agar. — Growth  slow.  Mycelium  fine,  aerial,  loose,  and  white, 
darkening  with  age.  Two  zones  formed,  but  not  very  distinct;  otherwise  like  the 
strain  from  carrot. 

On  Potato  Agar. — Growth  fair.  Mycelium  fine,  more  or  less  submerged,  and 
discoloring  the  medium  only  slightly.  No  zonation. 


380  BULLETIN  No.  189  [June, 

On  Agar  XII. — Growth  rapid.  Mycelium  somewhat  tufted  and  dense.  Three 
distinct  zones  present. 

"BEET" 

On  Green-Bean  Agar. — Growth  good.  Mycelium  flat  and  compact.  Several 
Hones  present. 

' '  BEGONIA  ' ' 

On  Corn-Meol  Agar. — Growth  fair.  Mycelium  rather  compact  and  white.  No 
zonation. 

On  Green-Bean  Agar. — Growth  fair.  Mycelium  white,  tufted,  and  compact. 
Zonation  indistinct. 

On  Potato  Agar. — Growth  fair.  Mycelium  compact,  dense,  and  white;  me- 
dium turning  dark.  Zonation. 

On  Agar  XII. — Growth  scant.  Mycelium  white,  fine,  and  loose.    No  zonation. 

' '  CARNATION  U.K." 

On  Corn-Meal  Agar. — Growth  good.  Mycelium  white,  making  a  rather  dense 
growth  for  corn-meal  agar.  Zonation  indistinct. 

On  Green-Bean  Agar. — Growth  good.    Like  strain  "Carnation  R.  H. " 

On  Oat  Avar — Growth  good.    Mycelium  white,  loose,  edge  tufted.  Zonation. 

On  Potato  Agar. — Growth  poor.  Mycelium  loo?e  and  scattering,  medium  turn- 
ing darker.  Zonation  indistinct. 

On  Agar  XII. — Growth  poor.  Mycelium  white,  loose,  and  scattered;  edge 
irregular.  Zonation  indistinct. 

"CARNATION  B.  H." 

On  Corn-Meal  Aaar. — Growth  fair.  Mycelium  white,  fine,  and  in  loose  strands ; 
rather  dense  at  center.  No  zonation. 

On  Grccn-Bcan  Agar. — Growth  good.  Mycelium  dark  at  center,  loose,  and 
tufted;  edge  irregular.  Zonation  very  characteristic  of  the  strains  isolated  from 
diseased  carnation  plants. 

On  Potato  Agar. — Growth  poor.  Mycelium  fine  and  scattered;  edge  irregular. 
Mycelium  causing  a  characteristic  browning  of  the  medium.  Zonation  indistinct. 

On  Agar  XII. — Growth  poor.  Mycelium  white,  fine,  loose,  and  scattered.  No 
zonation. 

"CARNATION  E.  S." 

On  Corn-Meal  Agar. — Growth  fair.  Mycelium  white,  fine,  but  rather  dense  at 
center;  edge  regular.  Zonation. 

On  Green-Bean  Agar. — Growth  good.  Mycelium  loose,  white,  and  tufted;  edge 
regular.  Later,  mycelium  turned  brown.  Zonation  somewhat  indistinct. 

On  Potato  Af;ar. —  Growth  poor  and  scant.  Mycelium  producing  a  distinct 
browning  of  the  agar.  Zones  indistinct. 

On  Agar  XII. — Growth  poor.    Mycelium  white,  scant,  loose,  and  flat.  Zonation. 

' '  CARNATION  E.  F. " 

On  Corn-Meal  Agar. — Growth  good.  Mycelium  white,  loose,  and  somewhat 
tufted.  No  zonatiou. 

On  Green-Bean  Agar.— Growth  fair.  Mycelium  white,  compact,  and  tufted. 
Zonation  somewhat  indistinct. 


1916]  PARASITIC  RHIZOCTONIAS  IN  AMERICA  381 

On  Oat  Agar. — Growth  good.    Mycelium  white,  loose,  flat,  and  fairly  dense; 
edge  tufted.    Zonal  ion. 

On  Potato  Agar. — Growth  poor.  Mycelium  scant,  like  that  produced  by  strains 
from  carnation. 

On  Potato-Glucose   Agar. — Growth   poor.    Mycelium   white,   loose,   scattered, 
and  somewhat  flaky ;  edge  very  irregular.    Zonation. 

On.  Agar  XII. — Growth  poor.    Mycelium  white,  fine,  loose,  flat,  and  scatter- 
ing; edge  very  irregular.    Zonation  indistinct. 

• 
' '  CARNATION  R.M.2 ' ' 

On  Corn  Meal  Agar. — Growth  good.    Mycelium  white,  tufted,  and  somewhat 
compact.    No  zonation. 

On  Green-Bean  Agar. — Growth  fair.    Mycelium  white,  tufted,  ard  compact. 
Zonation  indistinct. 

On  Oat  Agar. — Growth  fair.    Mycelium  white,  loose,  and  somewhat  flaky  at 
center;  edge  loose  and  irregular.    Zonation. 

On  Potato   Agar. — Growth  poor.    Mycelium  loose  and  fine.    Zonation  indis- 
tinct. 

On  Potato-Glucose  Agar. — Growth  fair.    Mycelium  brown,  loose,  und   flat; 
edge  loose  and  tufted.    No  zonation. 

On  Agar  XII. — Growth  fair.    Mycelium  white,  loose,  flat,  and  scattered.  No 
zonation. 

"CARNATION  B.D.C." 

On  Corn-Meal  Agar. — Growth  good.    Mycelium  white,  loose,  tufted,  and  rather 
dense.    No  Donation. 

On    Green  Tican    Agar. — Growth    good.     Mycelium   white,   loose,   tufted,    and 
dense.    Zonation  distinct. 

On  Oat  Agar. — Growth  fair.     Mycelium  white,  somewhat  dense  at  center,  and 
more  tufted  at  edge.    Zonation. 

On  Potato  Agar. — Growth  poor.    Mycelium  loose  and  flat,  darkening  slowly 
with  age.    Zoi.ation  indistinct. 

On  Potato-Glucose  Agar. — Growth  fair.     Mycelium  white,  flat,  and  flaky  at 
center.;   edge  loose  and  fluffy.     Zones  numerous  and  distinct. 

On  Agar  XII. — Growth  poor.   Mycelium  white,  somewhat  flaky  at  center;  edge 
irregular  an-1  scattered.   Zonation. 

' ' CARROT ' ' 

O.i  Corn-Meal  Agai. — Growth  good.  Mycelium  white,  fine,  and  somewhat  com- 
pact.   No  zonation. 

On   Green-Bean  Agar. — Growth  poor.    Mycelium   loose,   flat,   and  somewhat 
fluffy;  white  at  first,  followed  by  purplish  tinge.    Zonation  not  very  distinct. 

On  Oat  Agar. — Growth  fair.    Mycelium  white,  fine,  loose,  and  flat.    Zonation 
indistinct. 

On  Potato  Agar. — Growth  fair.    Mycelium  dark,  dense,  and  compact.    Zona- 
tion indistinct. 

On  Potato-Glucose  Agar. — Growth  fair.    Mycelium  dark,  loose,  flat,  and  flaky. 
Four  to  six  zones  present. 

On  Agar  XII. — Growth  slow.    Mycelium  white,  loose,  and  somewhat  flaky. 
Zonation. 


382  BULLETIN  No.  189  [June, 

1 '  CAULIFLOWER  ' ' 

On  Corn  Meal  Agar. — Growth  poor.    Mycelium  white,  loose,  and   scant.    No 
zonation. 

On  Green-Sean  Agar. — Growth  good.     Mycelium  white,  tufted,  and  compact; 
edge  regular.   Zonatioii. 

On  Oat  Agar. — Growth  good.    Mycelium  white,  fine,  loose,  flat,  and  dense, 
running  out  in  characteristic  strands.    No  zonation. 

On  Potato-Glucose  Agar. — Growth  fair.    Mycelium  dark,  loose,  flat,  and  flaky. 
One  zone  at  outer  edge. 

On  Agar  XII. — Growth  good.    Mycelium  white,  loose,  flat,  and  flaky.  Zonation. 

"  CHENOPODIUM  " 

On  Green-Bean  Agar. — Growth  good.    Mycelium  white,  flat,  radial,  and  com- 
pact.   No  zonation. 

"CLOVER  (RED)" 
On  Green-Bean  Agar. — Growth  good.  Mycelium  flat  and  compact.   Zonation. 

"COLEUS   I" 

On  Corn- Meal  A  gar. — Growth  good.    Mycelium  white,  loose,  and  somewhat 
compact.    No  zonal iou. 

On  Green-Bean  Agar. — Growth  good.    Mycelium  white,  tufted,  and  compact. 
Zonation  indistinct. 

On  Oat  Agar. — Growth  good.    Mycelium  white,  loose,  and  flat;   edge  fluffy. 
No  zonation. 

On  Potato  Agar. — Growth  fair.    Mycelium  loose  and  tufted,  turning  darker 
with  age.    No  zonation. 

On  Potato-Glucose  Agar. — Growth  fair.     Mycelium  dark,  loose,  and  flaky; 
edge  irregular.    Zonation. 

On  Agar  XII. — Growth  good.    Mycelium  loose,  dense,  and  white.   No  zonation. 

' ' CORN ' ' 

On  Corn-Meal  Agar. — Growth  poor.    Mycelium  white,  fine,  and  scattered.  No 
zonation. 

On  Green-Bean  Agar. — Growth  fair.  Mycelium  loose  at  edge  and  somewhat 
compact,  turning  darker  with  purplish  tinge.     Two  distinct  zones. 

On  Potato  Agar, — Growth  fair.    Mycelium  dense  and  compact.   Mycelium  and 
medium  turned  dark.     Zonation  indistinct. 

On  Agar  XII. — Growth  fair.   Mycelium  white,  loose,  tufted,  and  rather  dense 
at  center.    Zonation. 

"COTTON  I" 

On  Green-Bean  Agar. — Growth  fair.  Mycelium  loose,  tufted,  dense,  and  white. 
Two  zones  present.  •  . 

On  Oat  Agar. — Growth  good.     Mycelium  white,  loose,  flat,  dense,  and  radial, 
later  taking  on  a  wrinkled  appearance.     No  zonation. 

On  Potato-Glucose  Agar. — Growth  fair.    Mycelium  white,  flat,  dense,   flaky, 
and  regular;  loose  at  edge.    Zonation  indistinct. 


1916]  PARASITIC  EHIZOCTONIAS  IN  AMERICA  383 

On  Agar  XII. — Growth  fair.  Mycelium  flat,  somewhat  dense,  flaky,  and 
white  at  center;  edge  loose.  Two  distinct  zones. 

"COTTON  II" 

On  Green-Bean  Agar. — Growth  fair.  Mycelium  loose,  tufted,  and  fairly  dense, 
later  turning  brown.  Two  zones  present. 

On  Oat  Agar. — Growth  fair.  Mycelium  white,  fine,  loose,  and  flat,  forming  a 
mat  over  surface  of  the  medium.  One  zone  present. 

On  Potato-Glucose  Agar. — Growth  fair.  Mycelium  loose,  flat,  and  fairly  dense ; 
edge  irregular.  Later  both  mycelium  and  medium  turned  brown.  Two  zones 
present. 

On  Agar  XII. — Growth  fair.  Mycelium  white,  loose,  and  somewhat  tufted. 
Three  zones  present. 

"DlANTHUS  BARBATUS  N.P. " 

On  Green-Bean  Agar. — Growth  fair.  Mycelium  tufted  and  compact.  Zonation 
indistinct. 

"DlANTHUS  BARBATUS  S.M. " 

On  Green-Bean  Agar. — Growth  good.  Mycelium  tufted  and  compact.  Zona- 
tion rather  indistinct. 

' '  DlANTHUS  PLUMARIUS  ' ' 

On  Green-Bean  Agar. — Growth  good.  Mycelium  loose,  white,  and  somewhat 
tufted;  edge  regular.  Zonation  characteristic  of  the  carnation  strains. 

"DlANTHUS    SEQUERl" 

On  Green-Bean  Agar. — Growth  good.  Mycelium  loose,  white,  and  somewnut 
fluffy;  edge  regular.  Zonation  characteristic  of  carnation  strains  in  all  respects. 

' '  EGGPLANT  I ' ' 

On  Corn-Meal  Agar. — Growth  poor.  Mycelium  white,  fine,  and  mostly  sub- 
merged. No  zonation. 

On  Green-Bean  Agar. — Growth  good.  Mycelium  white,  flat,  radial,  compact, 
and  dense.  One  zone  at  center. 

On  Oat  Agar. — Growth  fair.  Mycelium  white,  loose,  flat,  interwoven,  and 
somewhat  tufted.  Zonation. 

On  Potato  Agar. — Growth  good.  Mycelium  dark,  compact,  dense,  and  radial. 
No  zonation. 

On  Potato-Glucose  Agar. — Growth  fair.  Mycelium  in  radial  strands,  flat,  and 
white.  No  zonation. 

On  Agar  XII. — Growth  fair.  Mycelium  white,  flat,  dense,  and  compact. 
One  zone  present. 

' '  GYPSOPHILA  ' ' 

On  Green-Bean  Agar. — Growth  fair.  Mycelium  white,  fluffy,  and  somewhat 
compact.  Zonation  very  characteristic  of  strains  from  carnation. 

' '  LAVATERA ' ' 

On  Green-Bean  Agar. — Growth  good.  Mycelium  white,  loose,  and  tufted;  edge 
even.  Several  zones  present. 


384  BULLETIN  No.  189  [June, 

"LETTUCE" 

On  Corn-Meal  Agar. — Growth  fair.  Mycelium  white,  fine,  slightly  aerial,  az<l 
somewhat  flaky.  No  zonation. 

On  Green-Bean  Agar. — Growth  good.  Mycelium  white,  loose,  flat,  and  rather 
dense,  running  out  in  strands.  One  indistinct  zone  present. 

On  Oat  Agar. — Growth  fair.  Mycelium  white,  loose,  flat,  interwoven,  and 
somewhat  tufted.  One  zone  present. 

On  Potato  Agar. — Growth  fair.  Mycelium  dark,  fine,  and  practically  all  sub- 
merged. No  zonation. 

On  Potato-Glucose  Agar. — Growth  good.  Mycelium  white  and  flat,  running 
out  in  radial  strands.  No  zonation. 

On  Agar  XII. — Growth  good.  Mycelium  white,  loose,  flat,  and  rather  dense. 
No  zonation. 

"ONION" 

On  Green-Bean  Agar. — Growth  fair.  Bright  colored  mycelium,  fine  and  sub- 
merged at  center;  a  little  aerial  mycelium  at  the  outer  edge,  where  it  was  some- 
what loose.  No  zonation. 

On  Potato  Agar. — Growth  fair.  Mycelium  fine,  scarcely  visible,  and  of  a 
bright  color.  No  zonation. 

On  Agar  XII. — Growth  fair.    No  aerial  mycelium.   No  zonation. 

"POIXSETTIA" 

On  Corn-Meal  Agar. — Growth  fair.  Mycelium  white,  dense,  fluffy,  and  com- 
pact. Zonation  indistinct. 

On  Green-Bean  Agar. — Growth  fair.  Mycelium  white,  loose,  compact,  and 
fluffy.  No  zonation. 

On,  Oat  Agar. — Growth  good.  Mycelium  white,  loose,  flat,  and  radial;  edge 
somewhat  fluffy.  No  zonation. 

On  Potato  Agar. — Growth  fair.  Mycelium  somewhat  flaky  and  compact.  Three 
zones  present. 

On  Potato-Glucose  Agar. — Growth  fair.  Mycelium  brown  and  flat  at  center; 
outer  edge  white,  loose,  and  somewhat  flaky.  Zonation  indistinct. 

On  Agar  XII. — Growth  fair.  Mycelium  white,  flat,  dense,  and  radial,  like 
alternanthera.  One  zone. 

"POTATO  R.  SOL." 

On  Corn-Meal  Agar. — Growth  fair.    Mycelium  fine  and  flat.    No  zonation. 

On  Green-Bean  Agar. — Growth  fair.  Mycelium  loose  at  edge,  compact  and 
fluffy  at  center.  Several  zones  present,  two  distinct. 

On  Potato  Agar. — Growth  fair.  Mycelium  white  and  fluffy.  One  zone  at  center. 

On  Agar  XII. — Growth  poor.  Mycelium  mostly  submerged  and  somewhat  com- 
pact; flaky  at  center.  Zonation. 

"POTATO  K.P.O." 

On  Corn-Meal  Agar. — Growth  fair.  Mycelium  white,  fine,  and  rather  scant. 
No  zonation. 

On  Green-Bean  Agar. — Growth  good.  Mycelium  loose  at  edge,  flat,  dense, 
somewhat  fluffy,  and  rather  dark.  Three  zones  present.  Growth  very  much  like 
strains  from  carnation. 


W16]  PARASITIC  BHIZOCTOXIAS  ix  AMERICA  385 

On  Potato  Agar. — Growth  fair.    Mycelium  dark,  loose,  and  fluffy.  Zonation 
distinct. 

On  Potato-Glucose  Agar. — Growth  fair.    Mycelium  white,  flat,  loose  at  edge, 
and  flaky  at  center.     Three  zones  present. 

On  Agar  XII. — Growth  very  slow.    Mycelium  white,  dense,  and  bushy,  form- 
ing a  tuft  at  the  center.    No  zonation. 

"SALVIA" 

On,  Green-Bean  Agar. — Growth  good.    Mycelium  white,  tufted,  and  compact. 
•Zonation  indistinct. 

On  Oat  Agar. — Growth  good.     Mycelium  white,  loose,  flat,  rather  dense,  and 
radial.   Zonation  indistinct. 

On  Potato-Glucose  Agar. — Growth  fair.   Mycelium  white  and  flaky  at  center; 
edge  loose  and  tufted.    Zonation  indistinct. 

On  Agar  XII. — Growth  good.   Mycelium  white  and  flaky  at  center;  edge  loose 
and  tufted.    Zonation  indistinct. 

"SEDUM" 

On  Green-Bean  Agar. — Growth  good.     Mycelium  flat  and  compact.    One  zone 
present.  ' 

' '  SUGAR  CANE  ' ' 

On  Corn-Meal  Agar. — Growth  fair.    Mycelium  white,  fine,  and  scarcely  visi- 
ble.    No  zonation.    . 

On  Green-Bean  Agar. — Growth  fair.   Mycelium  white,  loose,  and  tufted.  Zones 
present. 

On  Potato  Agar. — Growth  fair.    Mycelium  white,  fine,  and  practically  all  sub- 
merged. Two  indistinct  zones  present. 

On  Agar  XII. — Growth  fair.   Mycelium  white,  fine,  and  running  out  in  strands 
from  the  center.    No  zonation. 

"SWEET  PEA" 

On  Green-Bean  Agar. — Growth  good.    Mycelium  flat  and  compact.    One  zone 
present.     In  many  respects  like  strain  from  carnation. 

' '  THISTLE  ' ' 

On  Corn-Meal  Agar. — Growth  fair.    Mycelium  white,  running  out  in  strands; 
flat  at  center,  and  somewhat  loose  at  edge.     No  zonation. 

On  Green-Bean  Agar. — Growth  good.    Mycelium  white,  flat,  radial,  and  com- 
pact at  center;  edge  somewhat  loose  and  fluffy.     Zonation  indistinct. 

On  Oat  Agar. — Growth  good.    Mycelium  white,  flat,  dense,  and  radial.    No 
zonation. 

On  Potato  Agar. — Growth  fair.   Mycelium  white,  flat,  and  somewhat  compact, 
running  out  in  strands.     No  zonation. 

On  Potato-Glucose  Agar. — Growth  fair.   Characterized  by  a  white,  radial,  flat 
mycelium.     No  zonation. 

On  Agar  XII. — Growth  fair.   Mycelium  white,  flat,  compact,  and  flaky  at  cen- 
ter, becoming  looser  at  edge.     No  zonation. 


386  BULLETIN  No.  189  [June, 


BIBLIOGRAPHY 

1.  ANDERSON,  H.  W.     Carnation  Stem  Rot  Studies  at  Illinois.    Florists'  Rev., 

29,  746,  26-27.    1912. 

2.  .     Carnation  Stem  Rot.     Floriculture  Research  at  the  Experiment 

Station,  University  of  Illinois,  15-22.     1912. 

3.  ATKINSON,  G.  F.    Some  Diseases  of  Cotton.     Ala.  Sta.  Bui.  41,  30-39,  fig.  8. 

1892. 

4.  .     Damping-off.     N.   Y.    (Cornell)   Sta.  Bui.  94,  231-272,  fig.  55, 

6  pis.     1895. 

5.  .     Diseases  of  Cotton.     U.  S.  Dept  Agr.,  Office  Exp.  Stas.,  Bui.  33, 

292-293.     1896. 

6.  .     Studies  of  Some  Tree-Destroying  Fungi.     Trans.  Mass.  Hort. 

Soc.   (1901),  128-130.     1902. 

7.  BAILEY,  F.  D.     Lettuce  Diseases.     Ore.  Sta.  Bien.  Crop  Pest  and  Hort.  Rpt. 

(1911-12),  1,  275.    1913. 

8.  — .     Ehizoctonia  violacea  Tul.     Ore.  Sta.  Bien.  Crop  Pest  and  Hort. 

Rpt.  (1913-14),  2,  252-255,  fig.  26.     1915. 

9.  BARRUS,  M.  F.     Rhizoctonia  Stem  Rot  of  Beans.    Science,  n.s.,  33,  796.    1910. 

10.  BLAKE,  M.  A.,  AND  FARLEY,  A.  J.     Stem  Rot  of  Carnations.  N.  J.  Sta.  Rpt. 

(1910),  23,  78-81.   1911. 

11.  BULLIARD,  P.     Histoire  des  champignons  de  la  France.     1,  81.    Paris,  1791. 

12.  BURT,  E.A.     The  Thelephoracece  of  North  America  I.    Ann.  Mo.  Bot.  Gard., 

1,  193.     1914. 

13.  CARD,  F.  W.,  AND  ADAMS,  O.  E.     Carnation  Stem  Rot.     R.  I.  Sta.  Rpt.  (1898), 

12,  131-135,  1899:    (1899),  13,  249-251,  1900:    (1900),  14,  233-234,  1901. 

14.  CLINTON,  G.  P.     Report  of  Botanist.     Conn.  Sta.  Rpt.   (1903),  27,  279-370. 

1904. 

15.  -  — .  Report  of  Botanist.    Conn.  Sta.  Rpt.  (1906),  30,  324-325.    1906. 

16.  -              — .  Report  of  Botanist.     Conn.  Sta.  Rpt.  (1907-08),  31,  359.    1908. 
17. .  Report  of  Botanist.     Conn.   Sta.  Rpt.    (1911-12),  33,  348-349. 

1913. 

18.  COOK,  M.  T.     Diseases  Affecting  Potatoes.   Ann.  Rpt.  N.  J.  Bd.  Agr.  (1911), 

40,  155-161.     1912. 

19.  -  — .     Diseases  of  Tropical  Plants.     1913. 

20.  .     An  Ascomvcetous  Fungus  Associated  with  the  Rhizoctonia  of 

the  Potato.     Phytopath.,  4,  202-203,  fig.  2.     1914. 

21.  —  —  AND  MARTIN,  G.  W.     Potato  Diseases  in  New  Jersey,  N.  J.  Sta. 

Circ.  33,  10-12,  figs.  5  and  6.     1914. 

22.  CCONS,  G.  H.     The  Potato  Diseases  of  Michigan.    Mich.  Sta.  (Spec.)  Bui.  66, 

17-19,  figs.  5  and  6.     1914. 

23.  DE   BONDAROY,   FOUGEROUX.     Sur   le   safran.      Hist.    Acad.    Roy.   Sei.   Paris 

(1782),  89-112.     1785. 

24.  DE   CANDOLLE,   A.   P.      Memoire   sur   les    Rhizoctones.      Mem.   de   Museum 

d 'Histoire  Naturelle,  2,  209-219.     Paris,  1815.  t 

25.  DRAYTON,  F.  L.     The  Rhizoctonia  Lesions  on  Potato  Stems.    Phytopath.,  5, 

59-62,  pi.  6.     1915. 

26.  DUBY,  J.  E.     Botanicon  gallicum,  2  ed.,  867.     Paris,  1830. 

27.  DUGGAR,    B.    M.     Different    Types    of    Plant   Diseases   Due    to    a    Common 

Rhizoctonia.     Bot.  Gaz.,  27,  129.     1899. 

28.  — .     Three  Important  Fungous  Diseases  of  the  Sugar  Beet.     N.  Y. 

(Cornell)  Sta.  Bui.  163,  339-352,  figs.  49-55.     1899. 

29.  .     Fungous  Diseases  of  Plants.     444-452,  figs.  217-222;   477-479, 

fig.  239.     1909. 


1916]  PARASITIC  RHIZOCTOXIAS  IN  AMERICA  387 

30.  -  —  AND  STEWART,  F.  C.     Different  Types  of  Plant  Diseases  Due  to  a 

Common  Rhizoctonia.     Science,  n.s.,  9,  172.     1899. 

31.  —  .     A   Second  Preliminary  Report  on   Plant   Diseases 

Due  to  Rhizoctonia.     Science,  n.s.,  13,  249.     1901. 

32.  — .     The  Sterile  Fungus  Rhizoctonia  as  a  Cause  of  Plant 

Diseases  in  America.     N.  Y.    (Geneva)    Sta.  Bui.  186,  1-30,  figs.   15-23. 
1901.    N.  Y.  (Cornell)  Sta.  Bui.  186,  51-76,  figs.  15-23.    1901. 

33.  DUHAMEL,  H.  L.     Explication  physique  d  'une  maladie  qui  fait  perir  plusieurs 

plantes  dans  le  Gatinois  et  particulierment  le  safran.     Hist.  Acad.  Roy. 
Sci.  Paris  (1728),  100-112.     1728. 

34.  EARLE,  F.  S.     Diseases  of  Cotton.    Ala.  Sta.  Bui.  107,  295-296.    1899: 

35.  EDGERTON,  C.  W.,  AND  MORELAND,  C.  C.     Diseases  of  the  Tomato  in  Louisiana. 

La.  Sta.  Bui.  142,  1-23,  2  figs..    1913. 

36.  EDSON,  H.  A.     Damping-off  and  Root-Rot  Parasites  of  Sugar  Beets.   Phyto- 

path.,  3,  76.     1913. 

37.  ERIKSSON,  J.     Einige  Studien  iiber  den  Wurzeltoter.     (Rhizoctonia  violacca) 

der   Mohre   mit   besonderer   Rucksicht   auf    seine   Verbreitungsfahigkeit. 
Centbl.  Bakt.,  2  Abt.,  10,  721-738,  766-775,  1  pi.,  4  figs.   1903. 

38.  —  — .    Etudes    sur    la   maladie    produite   par   la    Rhizoctone    violacee. 

Rev.  Gen.  Bot.,  25,  14-30,  4  figs.    1913. 

39.  —          .     Work  of  the  Phytopathological  Section  of  the  Central  Agricul- 

tural Experiment  Station  in  Stockholm  in  1912.     Bui.  Bur.  Agr.  Intel, 
and  Plant  Diseases,  4,  1005.     1913. 

40.  FAWCETT,  H.  S.     Report  of  Plant  Pathologist,    Fla.  Sta.  Rpt.  (1909),  59-60. 

1909. 

41.  FRANK,  A.  B.     Ein  neuer  Rebenbeschadiger  in  Rheinhessen.    Ztschr.  Landw. 

Vereine  d.  Grossh.     Hessen,  19,  167.     1897. 

42.  FREEMAN,  G.  F.     Diseases  of  Alfalfa.     Kans.  Sta.  Bui.  155,  322-328.     1908. 

43.  FUCKEL,  L.     Symbolae  Mycologicoe,  142.     Wiesbaden,  1869. 

44.  FULTON,  H.  R.   Diseases  of  Peppers  and  Beans.   La.  Sta.  Bui.  101,  17,  fig.  14, 

1908. 

45.  ,  WRIGHT,  W.  J.,  AND  GREGG,  J.  W.     The  Control  of  Insects  and 

Diseases  Affecting  Horticultural  Crops.     Pa.  Sta.  Bui.  110,  27.     1912. 

46.  GLOVER,  T.     Accidents  and  Diseases  of  the  Cotton  Plant.     U.  S.  Dept.  Agr. 

Rpt.,  6,  pt.  3,  230-234.     1855-56. 

47.  GLOYER,  W.  O.     The  Efficiency  of  Formaldehyde  in  the  Treatment  of  Seed 

Potatoes  for  Rhizoctonia.    N.  Y.  (Geneva)  Sta.  Bui.  370,  417-431.     1913. 

48.  Gussow,  H.  T.     Potato  Scurf  and  Potato  Scab.     Jour.  Roy.  Agr.  Soc.  Eng- 

land, 66,  173-177,  1  pi.     1905. 

49.  — .     Beitrag  zur  Kenntnis  des  Kartoffel-Grindes.    Corticium  vagum 

(B.  &  C.)  var.  Solani  Burt.  Ztschr.  Pflanzenkrank.,  16,  135-137,  pi.  8.  1906. 

50.  -  — .    ' '  Rhizoctonia ' '    Disease    of    Potatoes.     Report    of    Dominion 

Botanist,  Canada  Expt,  Farms  Rpts.   (1912),  199-201.     1912. 

51.  HALLIGAN,   C.   P.     Celery  Culture   in    Michigan.      Mich.   Sta.    (Spec.)    Bui. 

60,  22.     1913. 

52.  HARTLEY,  C.     Notes  on  Some  Diseases  of  Coniferous  Nursery  Stock.  Science, 

n.s.,  31,  639.     1910. 

53.  — .     Damping-off  of   Coniferous  Seedlings.     Science,  n.s.,  36,   683. 

1912. 

54.  .     The  Use  of  Fungicides  to  Prevent  Damging-off.    Phytopath,  2, 

99.     1912. 

55.  -  — .  The  Blights  of  Coniferous  Nursery  Stock.    U.  S.  Dept.  Agr.  But. 

44,  17.     1913. 

AND  BBUNER,  S.  C.    Notes  on  Rhizoctonia.    Phytopath,  5,  73-75. 


1915. 


388  BULLETIN  No.  189  [June, 

57.  HEALD,  F.  D.  EJdzoctonia  viola cea  Tul.  on  Alfalfa.     Nebr.  Sta.  Bpt.   (1905), 

19,  40-60.    190G. 

58.  —  — .  Ehizoctonia  Medicaginis  DC.   in  America.     Phytopath.,  1,   103. 

1911. 

59.  AND  WOLF,  F.  A.     A  Plant-Disease  Survey  in  the  Vicinity  of 

San  Antonio,  Texas.    U.  S.  Dept.  Agr.,  Bur.  Plant  Indus.  Bui.  226,  1-129. 
1911. 

60.  HEDGCOCK,  G.  G.     A  Note  on  Khizoctonia.     Science,  n.s.,  19,  268.     1904. 

61.  HIBBARD,  R.  P.     Cotton  Diseases  in  Mississippi.     Miss.  Sta.  Bui.  140,  17-18, 

fig.  4.     1910. 

62.  HUME,  H.  H.    Potato  Diseases.    Fla.  Sta.  Bui.  75,  188-194,  pi.  1.     1904. 

63.  JOHNSON,  J.     The  Control  of  Damping-off  Disease  in  Plant  Beds.    Wis.  Sta. 

Research  Bui.  31,  29-61,  10  figs.     1914. 

64.  KUHN,   J.     Krankheiten   der  Kulturgewachse,   224-228,   figs.    17-21.     Berlin, 

1858. 

65.  LEVEILLE,  J.  H.     Memoire  sur  le  genre  Sclerotium.    Ann.  Sci.  Nat.  Bot.,  20, 

223.    Paris,  1843. 

66.  MASSEE,  G.     Diseases  of  Cultivated  Plants  and  Trees,  238.     1910. 

67.  McALPiNE,  D.     Handbook  of  Fungous  Diseases  of  the  Potato  in  Australia 

and  Their  Treatment.     Dept.  Agr.  Victoria,  Melbourne,  1-215.     1912. 

68.  MORSE,  W.  J.     Powdery  Scab  of  Potatoes.     Me.  Sta.  Bui.  227,  97-98,  figs. 

51-52.    1914. 

69.  —  AND  SHAPOVALOV,  M.     The  Rhizoctonia  Disease  of  Potatoes.  Me. 

Sta.  Bui.  230,  193-216,  figs.  61-73.     1914. 

70.  NEES  VON  ESENBECK,  T.     System  der  Pilze  und  Schwamme,  148,  fig.  135. 

Wiirzburg,  1817. 

71.  ORTON,  W.  A.     Potato  Diseases  in  San  Joaquin  County,  California.     U.  S 

Dept.  Agr.,  Bur.  Plant  Indus.  Circ.  23,  8.     1909. 

72.  —  — .     Tomato  Diseases.    Tracy  Tomato  Culture.    131-147.     1910. 

73.  .     Potato-Tuber  Diseases.     U.  S.  Dept.  Agr.,  Farmers'  Bui.  544, 

6-7,  fig.  3.    1913. 

74.  —  — .     Potato  Wilt,  Leaf-roll,  and  Related  Diseases.    U.  S.  Dept.  Agr. 

Bui.  64,  40-41,  pi.  15.    1914. 

75.  PADDOCK,  W.     Plant  Diseases  of  1901.    Colo.  Sta.  Bui.  69,  1-23,  pi.  3 ;  pi.  5, 

fig.  3;  pi.  6,  fig.  1. 

76.  PAMMEL,  L.  H.     Fungous  Diseases  of  Sugar  Beets.    la.  Sta.  Bui.  15,  244-251 

pis.  3-4.     1891. 

77.  PELTIER,  G.  L.     Experiments  with  Carnation  Stem  Rot.    Amer,  Florist,  40, 

1292,  324-327.     1913. 

78.  -  — .     Carnation  Diseases.     Florists'  Ex.,  37,  5,  252-253,  fig.  1.     1914. 

79.  —  — .     Carnation  Diseases.    Amer.  Florist,  42,  1346,  432-434.     1914. 

80.  .     Rhizoctonia  in  America.     Phytopath.,  4,  406,    1914. 

81.  -  — .    Stem  Rot  of  Carnations.    Florists'  Ex.,  39,  10,  539.     1915. 

82.  PERSOON,  C.  H.     Synopsis  methodica  fungorum,  119.     Gottingse,  1801. 

83.  PETHYBRIDGE,  G.  H.    Investigations  on  Potato  Diseases  in   Ireland.     Dept. 

Agr.  and  Tech.  Instr.  Ireland  Jour.,  11,  417-449.     1911. 

84.  — .     Potato  Diseases  in  Ireland.     Dept.  Agr.  and  Tech.  Instr.  Ire- 
land Jour.,  10,  241-256.     1930. 

85.  .     Rotting  of  Potato  Tubers  by  New  Species  of  Phytophora  Hav- 
ing a  New  Method  of  Sexual  Reproduction.  Sci.  Proc.  Roy.  Dublin  Soc., 
n.s.,  13,  35.     1913. 

86.  POOL,  V.  W.     Some  Tomato  Fruit  Rots  in  1907.     Nebr.  Sta.  Rpt.  (1907),  21, 

6-9,  figs.  10-22.     1908. 


1916]  PARASITIC  EHIZOCTOXIAS  IN  AMERICA  389 

87.  FRILLIEUX,  E.     Sur  la  penetration  de  la  Ehizoctone  violette  dans  les  racines 

de  tetterave  et  de  luzerne.  Bui.  Soc.  Bot.  France,  43,  9-11.     1896. 

88.  .     Maladies  des  plantes  agrieoles,  2,  144-157.,  figs.  282-287.    Paris, 

1897. 

89.  —  -    AND   DELACROIX,   G.      Hiipochmts   Solani.   Nov.    sp.      Bui.    Soc. 

Mycol.  France,  7,  220-221,  1  fig.    1891. 

90.  PRUNET,  A.     Sur  le  Ehizoctone  de  la  luzerne.    Compt.  Eend.  Acad.  Sci.  Paris, 

117,  252-255.    1894. 

91.  EEUTER,  B.     Berattelse  b'fver  skadeinsekters  uppertradande  i  Finland  ar  1897. 

Landt  bruksstyrelsens  neddelander,  23,  1-70.    1898. 

92.  EOLFS,  F.  M.     Potato  Failures.     Colo.  Sta.  Bui.  70,  1-20,  12  pis.     1902. 

93.  —  — .     Corticium  vagum  B.  &  C.,  var.  Solani  Burt.     A  Fruiting  Stage 

of  Bhizoctonia  Solani.    Science,  n.s.,  18,  729.     1903. 

94.  -  — .     Potato  Failures.    Colo.  Sta.  Bui.  91,  1-33,  5  pis.     1904. 

95.  -  — .     Beport  of  Horticulturist.     Fla.  Sta.  Ept.   (1905),  29-47.     1905. 

96.  BOSTRUP.  E.     Oversigt  over  indlobene  Foresporgsler  angoaaende  Sygdomme 

hos  Kulturplanter.     Tidsskr.  for  Landokonomi,     Nos.  1-9.     Kjobenhavn, 
1884-1893. 

97.  —  — .      Oversigt      over     Landbrugsplanternes      Sygdomme.        Tidsskr. 

Handbrugets  Planteavl.,  Nos.  1-12.     Kjobenhavn,  1894-1905. 

98.  EOZE,   E.     Observations  sur  le   Bhizoctone   de  la  pomme   de   terre.     Compt. 

Bend.  Acad.  Sci.  (Paris),  123,  1017-1019.     1896. 

99.  — .     Sur   les   maladies   des   bulbs    du   safran    (Crocus  sativus   L.). 

Compt.  Eend.  Acad.  Sci.   (Paris),  125,  730-732.    1897. 

100.  — .     La  maladie  de  la  gale  de  la  pomme  de  terre  et  ses  rapports  avec 

le  Bhizoctonia  Solani  Kiihn.      Bui.  Soc.  Mycol.  France,  13,  23-28.    1897. 

101.  SALMON,  E.  S.     Diseases  of  Seakale.     Gard.  Chron.,  103,  1,  3  figs.    1908. 

102.  SELBY,  A.  D.     A  Disease  of  Potato  Stem  in  Ohio  Due  to  Bhizoctonia.  Science, 

n.s.,  16,  138. 

103.  .     A   Eosette   Disease  of  Potatoes.      Ohio   Sta.   Bui.    139,   53-66, 

5  figs.     1903. 

104.  .     Studies  in  Potato  Eosette  II.     Ohio  Sta.  Bui.  145,  15-28,  4  figs. 

1903. 

105.  -          .     Tobacco  Diseases  and  Tobacco  Breeding.     Ohio  Sta.  Bui.   156, 

97-99,  pi.  1.    1904. 

106.  .     Soil   Treatment  for  the   Forcing  House.     Ohio   Sta.   Circ.  57, 

1-9,  2  figs.     1906. 

107.  — .     Soil  Treatment  of  Tobacco-Plant  Beds.     Ohio   Sta.  Circ.  59, 

1-3,  fig.  1.     1906. 

108.  .     A  Brief  Handbook  of  the  Diseases  of  Cultivated  Plants  in  Ohio. 

Ohio  Sta.  Bui.  214,  307-456.     1910. 

109.  SHAW,   F.   J.   F.     The   Morphology   and   Parasitism   of   Ehizoctonia.      Mem. 

Dept.  Agr.  India,  Bot.  Ser.,  4,  No.  6,  115-153,  5  figs,  11  pis.     1912. 
130.  SHEAR,  W.  V.     Potato  Growing  in  the  San  Joaquin  and  Sacramento  Deltas 
of  California.    Gal.  Sta.  Circ.  120,  4-5,  figs.  2-3.     1914. 

111.  SIRRINE,  F.  A.     Some  Causes  of  Poor  Stands  of  Potatoes.     N.  Y.  Dept.  Agr. 

Bui.  57,  1082.     Albany,  1914. 

112.  SMITH,  B.  E.     Beport  of  Plant  Pathologist  to  July  1,  1906.     Cal.  Sta.  Bui. 

184,  253.     1907. 

113.  — .     Beport  of  Plant  Pathologist,  July  1,  1906,  to  June  30,  1909. 

Cal.  Sta.  Bui.  203,  60.     1909. 

114.  AND  SMITH,  E.  H.    California  Plant  Diseases.    Cal.  Sta.  Bui.  218, 

1039-1193,  figs.  66,  81,  90.     1911. 

115.  STAKMAN,  E.   C.,  AND   TOLAAS,  H.  G.     Potato  Diseases.     Minn.   Sta.    Ext. 

Bui.  35,  12-14,  fig.  7.     1912. 


390  BULLETIN  No.  189  [June, 

116.  STEVENS,  F.  L.     Two  Interesting  Apple  Fungi.    Science,  n.s.,  26,  724.     1907. 

117.  —  AND  HALL,  J.  G.    Hypochnose  of  Pomaceous  Fruit.  Ann.  Mycol., 

7,  47-59,  8  figs.     1909. 

118. .     Diseases   of   Economic  Plants,    87-91,   figs.   34-35. 

1910. 

119.  .     Hypochnose  of  Pomaceous  Fruits.     N.  C.  Sta.  Rpt. 

(1908-1909),  32,  76-85,  figs.  41-48.     1911. 

120.  STEVENS,   F.   L.,  AND  WILSON,   G.    W.     Ehizoctonia   of  Buckwheat.     Jour. 

Elisha  Mitchell  Sci.  Soc.,  27-84.     1911. 

121.  .     Ehizoctonia  of  Buckwheat.     Science,  n.s.,  33,  943. 

1911. 

122.  .     Clover  Rhizoctonia.     N.  C.  Sta.  Rpt.   (1910),  34, 

70-73.     1911. 

123.  STEWART,  F.  0.     The  Stem  Rot  of  Carnations.     Science,  n.s.,  9,  172.     1899. 

124.  -  — .     The  Stem  Rot  of  Carnations.    Bot.  Gaz.,  27,  129.     1899. 

125.  -  — .     Notes  on  New  York  Plant  Diseases  I.     N.  Y.   (Geneva)    Sta. 

Bui.  328,  383-386.     1910. 

126.  ,  FRENCH,  A.  T.,  AND  WILSON,  J.  K.    Troubles  of  Alfalfa  in  New 

York.    N.  Y.  (Geneva)  Sta.  Bui.  305,  392-393.    1908. 

127.  STIFT,  A.     Zur  Geschichte  des  Wurzeltb'ters  oder  der  Rotfaule    (Ehizoctonia 

violacea).  C»sterr.  Ungar.  Zeitschr.  Zucherindus.  u.  Landw.,  42,  445-461. 
1913. 

128.  STONE,  G.  E.,  AND  SMITH,  R.  E.     The  Rotting  of  Greenhouse  Lettuce.     A 

Rhizoctonia  Disease  of  Lettuce.     Mass.    (Hatch)    Sta.   Bui.   69,   16-17, 
figs.  9-10.     1900. 

129. .   Report   of   Botanist.      Mass.   Sta.  Rpt.    (1901),  33, 

66-69.     1902. 

130.  TAUBENHAUS,  J.  J.     Diseases  of  the  Sweet  Pea.     Gard.  Chron.,  54,  22-23, 

figs.  11-12.     1912. 

131.  .     The  Diseases  of  the  Sweet  Pea.    Del.  Sta.  Bui.  106,  18-24,  figs. 

9-11.     1914. 

132.  TEMPLE,  C.  E.     Potato  Diseases.    Idaho  Sta.  Bui.  79,  44-45,  fig.  3.     1914. 

133.  THOMPSON,  H.  C.     Control  of  Diseases  of  Fruits,  Vegetables,  and  Flowers. 

Miss.  Sta.  Bui.  141,  28.     1910. 

134.  TULASNE,  L.  R.,  AND  TULASNE,  C.     Fungi  Hypogsei.     188-195.     Paris,  1851. 

135.  VAN  HOOK,  J.  M.     Diseases  of  Ginseng.     N.  Y.    (Cornell)    Sta.   Bui.  219, 

174-176,  figs.  32-33.     1904. 

136.  -  — .     Celery  Root  Rot.    Ohio  Sta.  Circ.  72,  1-6,  3  figs.    1907. 

137.  WEBBER,  H.  J.     Catalog  of  the  Flora  of  Nebraska.     Rpt.  Nebr.  State  Bd. 

Agr.   (1889),  76.     1890. 

138.  WHETZEL,  H.  H.,  AND  ROSENBAUM,  J.     The  Diseases  of  Ginseng  and  Their 

Control.     U.  S.  Dept.  Agr.,  Bur.  Plant  Indus.  Bui.  250,  23,  fig.  2.     1912. 

139.  WINSTON,  J.  R.     Effects  of  the  Steam-Formalin  Treatment  on  Certain  Soil 

Organisms.     Phytopath.,  3,  74.     1913. 

140.  WOLF,  F.  A.     Fruit  Rots  of  Eggplant.     Phytopath.,  4,  38.     1914. 

141.  — .     Eggplant  Rots.    Mycol.  Centbl.,  4,  278-287,  figs.  3-4,  1914. 

142.  WOLLENWEBER,   H.  W.  Pilzparasitare   Welkekrankheiten   der   Culturpflanzen. 

Ber.  Deut.  Bot.  Gesell.,  31,  30.    1913. 


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